* There might be a bug in the software, I think you need to check the new version or report the bug
in the community developer.
If there's a bug in the software; if not all, most of the users will experience that issue.
Only suggest to report a bug once the issue is confirmed, otherwise there'll be lots of false reports that could waste the developers' time.
* Probably, your wallet maybe locked.
Bitcoin Core's wallets can be used and generate receiving addresses even when locked.
* There is also a case where your wallet possibly in a "WATCHING ONLY MODE"
In this case, you are free to view your transaction records also your balance, but you can't able to
send bitcoin and can't able to create a new address too. Therefore, you need to change it into
"FULL MODE", and for you to do this you need to paste your private keys.
Watching-only wallet in Bitcoin Core can produce new receiving addresses.
Note: It's best for the OP, the forum and for you if you test your hypothesis first before posting them.