There are a couple of queries from earlier on this subject but thought I'd try to get up-to-date suggestions if there are any. The last time I needed to use a BT wifi hotspot was two years ago, and it worked. I thought I might need to use one again last week, so, belt and braces, I thought I'd just check the situation and I simply cannot log in - it just keeps asking me to check that username and password are correct. I've used current and old passwords (because I have changed passwords since I last used a hotspot) to no avail. I do not wish to end up in worse position that I am now because email and my BT both work fine, the only problem is logging into a wifi hotspot, so I do not wish or intend to change my password again. (Could it be the username, possibly not needing the @btetc suffix?)
Are you using the BTWifi app or are you trying to log on directly with a web browser.
If using the BTWifi app try using a web browser.
See help pages and assuming you are a BT broadband customer follow the BT Broadband prompts for what ever device system you are using.
Get wireless Internet | Find wi-fi hotspots | BT Wi-Fi (btwifi.co.uk)
If you get logged on that way you will know that it is an app problem.
If you still can not log on it may be that the system has the "wrong" password recorded against your user name and it may need further assistance to get that corrected.