Dear @Wilhelm_Tomasi ,
the location permission shall be granted for a proper BT comm's, as well as the BT itself.
This is an Android/Google policy (but don't ask me why 
).
It is not clear your statement: "it used to work before". Do you mean that a previous version of your app was already working as .apk ? if yes, then some questions arise:
-have you changed your phone?
-have you updated the Android version on your phone ?
-is still your phone paired with the Arduino (Nano33) system ?
-are you sure about the UUID's ?
In addition to these doubts, with the aim of verifying if the communication is still working (also including the Nano side) please use the Serial Bluetooth Terminal app (free on Playstore) so to discriminate where is the problem (i.e. Nano or App).
Last hint, fro the moment: it s not only necessary to ask for permission, but before attempting a communication you shall ckeck for "permission granted", else any attempt to start a communication will not work.
A rich library of case-studies can be found in the FAQ (thanks to @Abg) :
Best wishes