PookaMustard: Do you actually have a keyboard enabled on your Android? Go to Settings -> Language and input, and see if any of the keyboards you installed are enabled.
I will also suggest a restart.
In the meantime, I will see if GOG.com reviews can work via Chromer.
FINAL EDIT: Yes, I'm also experiencing the same issue. You can always remedy that via pasting your review text, which somehow works. However I can't tell you whether you can post a review this way, as reviews can't be deleted.
BONUS EDIT: On UC Browser, you can hold the textboxes and tap on "Long text input" which will show you a dedicated textbox to write your review into. Tapping the GOG textbox straight away will refuse to work. Also on Chromer, it is hard to choose your rating as they disappear the instant you call them, but not the case on UC Browser.
Thanks for taking the time to check all that Pooka , much appreciated, I'll post it later on my laptop, cheers! :)
F1ach: I'm on chrome, I don't know what a PCMR is tbh :) Cool at least I'm not the only one :)
+1s and thanks for the replies guys :)
Smannesman: PC Master Race I'm guessing.