RN214 app install failure - 403 forbidden

Attempting to install apps results in an error stating:

Apps operation failed.

Application <app name> cannot be installed.

In /var/log/readynasd/install_debpkg.log file I see the following:

Install app nastools-netdata
fv-app-install-utils.c:101(info) [nastools-netdata](0%) prepare
fv-app-install-utils.c:106(info) Downloading [nastools-netdata](0%) Retrieving file 1 of 1
fv-app-install-utils.c:106(info) Downloading [nastools-netdata](0%) Retrieving file 1 of 1
fv-app-install-utils.c:106(info) Downloading [nastools-netdata](0%) Retrieving file 1 of 1
fv-app-install-utils.c:106(info) Downloading [nastools-netdata](0%) Retrieving file 1 of 1
fv-app-install-utils.c:106(info) Downloading [nastools-netdata](0%) Retrieving file 1 of 1
fv-app-install-utils.c:106(info) Downloading [nastools-netdata](0%) Retrieving file 1 of 1
fv-app-install-utils.c:106(info) Downloading [nastools-netdata](0%) Retrieving file 1 of 1
fv-app-install-utils.c:106(info) Downloading [nastools-netdata](0%) Retrieving file 1 of 1
fv-app-install-utils.c:106(info) Downloading [nastools-netdata](0%) Retrieving file 1 of 1
fv-app-install-utils.c:106(info) Downloading [nastools-netdata](0%) Retrieving file 1 of 1
fv-app-install-utils.c:106(info) Downloading [nastools-netdata](0%) Retrieving file 1 of 1
fv-app-install-utils.c:106(info) Downloading [nastools-netdata](0%) Retrieving file 1 of 1
fv-app-install-utils.c:106(info) Downloading [nastools-netdata](0%) Retrieving file 1 of 1
fv-app-install-utils.c:106(info) Downloading [nastools-netdata](0%) Retrieving file 1 of 1
fv-app-install.c:674(error) fv-app-install (nastools-netdata): error code [100]: Reading package lists...
Building dependency tree...
Reading state information...
The following NEW packages will be installed:
  nastools-netdata
0 upgraded, 1 newly installed, 0 to remove and 31 not upgraded.
Need to get 1,753 kB of archives.
After this operation, 5,963 kB of additional disk space will be used.
Err:1 https://apt.readynas.com/packages/readynasos 6.10.4/apps armel nastools-netdata armel 1.4.0-nt1
  403  Forbidden
E: Failed to fetch https://apt.readynas.com/packages/readynasos/dists/6.10.4/apps/pool/n/nastools-netdata/nastools-netdata_1.4.0-nt1_armel.deb  403  Forbidden

E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

fv-app-install-utils.c:121(info) [nastools-netdata](0%) abort

This seems similar to other issues reported in the past, as late as RN 6.10.3. I'm presently running 6.10.4 Hotfix 1.