AC2200 Nighthawk X4 has 5G working but not 2G working

Hey, I saw something posted about this for the R7000 but it didn't help with my issue because the firmware isn't what I need. I've been trying for two days constantly to see why 2GEXT would be available to use but had no internet connection, but the 5GEXT worked fine.

The original modem was given to us from Telstra when we asked to upgrade to NBN.

With the extender (AC2200 Nighthawk X4), I've been doing a factory reset, then I would connect to the extender (which is near the original modem) via my laptop(Windows 10) and set it up with the modem, to which it says that everything was successful, 2GEXT wouldn't work, but 5GEXT did work. I've also tried connecting the extender to the modem via WPS and that has also had the same outcome. Connecting the two via ethernet cable has worked fine, but isn't helpful because the range is still low where my room is.

I find this a problem because my PS4 and the family computer are a bit old and don't have access to 5G internet, it is becoming a hassle for everyone in the family.

The original modem works fine with both 2G and 5G, but the range isn't far enough to reach the back of the house, so we hoped that the extender would help out. It did, it was fantastic for my phone and laptop (because they could connect to 5GEXT) but wasn't good when I tried it on my PS4 and the PC.

I'm hoping that I can find a solution because my little brother and sister have assignments coming up and need to do some of it online, and the family computer is their only option.

We bought the extender at JB-Hi-Fi for about $300 with it all tightly sealed and safe, the model number is EX7300 if that helps.

Any help would be fantastic, thank you :)