New drive not being used in RAID, management service offline

Im using a ReadyNAS202 running 2 x 2TB WD red drives

I noticed my Time Machine backups were starting to fail and then realised one of my disks was degraded. I replaced that with a new one earlier today and now both disks are fine, but Raidar diagnostics is showing I have some serious sounding issues now:

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Volume root is degraded
Volume 1 is inactive
Volume data is degraded

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And I can't load the management service in the browser. What is surprising to me is that time machine backups from my mac are continuing to be successful.

I've tried a firmware reinstall but that hasn't helped.

mdstat.log seems to show that only one of my drives is being used in raid1?

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Personalities : [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
md127 : active raid1 sda3[1]
1948662784 blocks super 1.2 [2/1] [_U]

md1 : active raid1 sda2[0]
523264 blocks super 1.2 [2/1] [U_]

md0 : active raid1 sda1[1]
4190208 blocks super 1.2 [2/1] [_U]

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Both disks are showing as fine in volume.logs but then only one shows in my Raid Arrays, is this highlighting the issue?

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Enclosures
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Enclosure 0:
Disks:
sda:
HostID: 1165474c
Flags: 0x0
Size: 3907029168 (1863 GB)
Free: 4062
Controller 0
Channel: 0
Model: WDC WD20EFRX-68EUZN0
Serial: WD-WCC4M7KVED4V
Firmware: 82.00A82W
Class: SATA (2)
RPM: 5400
SMART data
Reallocated Sectors: 0
Reallocation Events: 0
Spin Retry Count: 0
Current Pending Sector Count: 0
Uncorrectable Sector Count: 0
Temperature: 40
Start/Stop Count: 184
Power-On Hours: 55883
Power Cycle Count: 184
Load Cycle Count: 757
Latest Self Test: Passed

sdb:
HostID: 00000000
Flags: 0x0
Size: 3907029168 (1863 GB)
Free: 3897591886
Controller 0
Channel: 1
Model: WDC WD20EFZX-68AWUN0
Serial: WD-WX42D61CHAJ5
Firmware: 81.00B81W
Class: SATA (2)
RPM: 5400
SMART data
Reallocated Sectors: 0
Reallocation Events: 0
Spin Retry Count: 0
Current Pending Sector Count: 0
Uncorrectable Sector Count: 0
Temperature: 35
Start/Stop Count: 4
Power-On Hours: 0
Power Cycle Count: 4
Load Cycle Count: 2
Latest Self Test: Passed

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RAID arrays
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RAID 0:
Device: md0
HostID: 1165474c
UUID: 75815115-ac80-d804-3413-67ae26990607
Size: 8380416
Component size: 8388608
Class: SATA (2)
Level: 1
State: degraded
Action: idle
Flags 0x28
Members: 2
Pool: root
Disks:
sda:
HostID: 1165474c
Flags: 0x0
Size: 3907029168 (1863 GB)
Free: 4062
Controller 0
Channel: 0
Model: WDC WD20EFRX-68EUZN0
Serial: WD-WCC4M7KVED4V
Firmware: 82.00A82W
Class: SATA (2)
RPM: 5400
SMART data
Reallocated Sectors: 0
Reallocation Events: 0
Spin Retry Count: 0
Current Pending Sector Count: 0
Uncorrectable Sector Count: 0
Temperature: 40
Start/Stop Count: 184
Power-On Hours: 55883
Power Cycle Count: 184
Load Cycle Count: 757
Latest Self Test: Passed

RAID 1:
Device: md1
HostID: 1165474c
UUID: 0dfee7f7-0666-a1e9-a3a5-cb05015fede0
Size: 1046528
Component size: 1048576
Class: SATA (2)
Level: 1
State: degraded
Action: idle
Flags 0x28
Members: 2
Pool: 1
Disks:
sda:
HostID: 1165474c
Flags: 0x0
Size: 3907029168 (1863 GB)
Free: 4062
Controller 0
Channel: 0
Model: WDC WD20EFRX-68EUZN0
Serial: WD-WCC4M7KVED4V
Firmware: 82.00A82W
Class: SATA (2)
RPM: 5400
SMART data
Reallocated Sectors: 0
Reallocation Events: 0
Spin Retry Count: 0
Current Pending Sector Count: 0
Uncorrectable Sector Count: 0
Temperature: 40
Start/Stop Count: 184
Power-On Hours: 55883
Power Cycle Count: 184
Load Cycle Count: 757
Latest Self Test: Passed

RAID data-0:
Device: md127
HostID: 1165474c
UUID: 62a98689-50b1-62e3-6603-f2ccdff36d4a
Size: 3897325568
Component size: 3897587824
Class: SATA (2)
Level: 1
State: degraded
Action: idle
Flags 0x8
Members: 2
Pool: data
Disks:
sda:
HostID: 1165474c
Flags: 0x0
Size: 3907029168 (1863 GB)
Free: 4062
Controller 0
Channel: 0
Model: WDC WD20EFRX-68EUZN0
Serial: WD-WCC4M7KVED4V
Firmware: 82.00A82W
Class: SATA (2)
RPM: 5400
SMART data
Reallocated Sectors: 0
Reallocation Events: 0
Spin Retry Count: 0
Current Pending Sector Count: 0
Uncorrectable Sector Count: 0
Temperature: 40
Start/Stop Count: 184
Power-On Hours: 55883
Power Cycle Count: 184
Load Cycle Count: 757
Latest Self Test: Passed

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In disk_info.log I'm noticing the new drive is not showing pool type as RAID1 etc, is there something I need to do?

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Device: sda
Controller: 0
Channel: 0
Model: WDC WD20EFRX-68EUZN0
Serial: WD-WCC4M7KVED4V
Firmware: 82.00A82W
Class: SATA
RPM: 5400
Sectors: 3907029168
Pool: data
PoolType: RAID 1
PoolState: 3
PoolHostId: 1165474c
Health data
ATA Error Count: 0
Reallocated Sectors: 0
Reallocation Events: 0
Spin Retry Count: 0
Current Pending Sector Count: 0
Uncorrectable Sector Count: 0
Temperature: 40
Start/Stop Count: 184
Power-On Hours: 55883
Power Cycle Count: 184
Load Cycle Count: 757

Device: sdb
Controller: 0
Channel: 1
Model: WDC WD20EFZX-68AWUN0
Serial: WD-WX42D61CHAJ5
Firmware: 81.00B81W
Class: SATA
RPM: 5400
Sectors: 3907029168
Health data
ATA Error Count: 0
Reallocated Sectors: 0
Reallocation Events: 0
Spin Retry Count: 0
Current Pending Sector Count: 0
Uncorrectable Sector Count: 0
Temperature: 35
Start/Stop Count: 4
Power-On Hours: 0
Power Cycle Count: 4
Load Cycle Count: 2

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I can SSH onto the NAS, there doesn't seem to be anything alarming in terms of disk usage, otherwise I'm not sure what to look for

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root@TXHReadyNAS:/# df -h
Filesystem Size Used Avail Use% Mounted on
udev 10M 4.0K 10M 1% /dev
/dev/md0 3.7G 736M 2.8G 21% /
tmpfs 1009M 4.0K 1009M 1% /dev/shm
tmpfs 1009M 412K 1009M 1% /run
tmpfs 505M 920K 504M 1% /run/lock
tmpfs 1009M 0 1009M 0% /sys/fs/cgroup
/dev/md127 1.9T 983G 875G 53% /data
/dev/md127 1.9T 983G 875G 53% /home
/dev/md127 1.9T 983G 875G 53% /apps