I haven’t seen this scenario yet, but so far, as I read before, there aren’t issues with IP blocking to access the vault. That is, did it warn you that your IP address was blocked on a pop up message?
Anyway, I’d advise you to do this:
- Clear the app data and start from a fresh 1st run
- If it doesn’t work, try uninstalling and reinstalling the app again. The could make sure that it is not related to your device.
By any means, if only your phone got its IP blocked, try using a VPN service, such as ProtonVPN to test things and make sure your external IP address is blocked indeed.
Also, I’d recommend you to take a look on the posts tagged with this search criteria:
https://community.bitwarden.com/search?q=offline
And this also talks a bit more about how accessing your vault offline works.