Same info goes to you. Have you ever used passport/ID from outside of the UK? IF so, likely is your issue.
I know you said you originally made the account in the UK, but that’s a different question. Only have to ask as we’ve had people who said originally created in places like the UK but their passports were from places like India, which is not supported. So for them to be helped, they had to update their documentation with Uphold as I mentioned in the linked post.
EDIT
Just was reading again before moving on. Just noticed you said:
It has been happening for 3 weeks and only happens on my PC. On my phone I was able to log in on the very same IP.
I want to be clear that your IP address has absolutely nothing to do with you being in an unsupported region. This would only apply to your information in Uphold. So both your photo ID/passport you used for KYC as well as everything you have reported in your Profile.
When you’re saying that your phone was able to log in, was that recent or are you just saying it’s connected from beforehand? Because anything connected prior to Brave stopping support will remain connected until you disconnect it or it logs out automatically within 90-120 days. Then once disconnected, you’d no longer be able to connect it again until your Uphold account reflects info to Brave that shows you live in a supported region (and have the passport/ID updates showing you there, and not another country)
Sorry, almost wall of text here. But really will help if you can clarify when you were able to connect your other devices, if that passport/ID might be from outside the UK, etc. If it is just an oddball situation, we’ll have to get someone from Brave to help you. But if it is an issue where it’s a mismatch of documentation at Uphold and your other devices just are connected from before, then it would be Uphold that’s needing to make changes.