How to fix SipgateFFX: Your login information is wrong
The SipgateFFX is quite a cool addon. But it doesn't exactly give you a lot of feedback.
After some trial and error I discovered that if you have a regular individual account, you need to deselect 'I'm using sipgate team'.
Your username is your Sipgate website username, not your SIP ID, and the password is your Sipgate website password, not your SIP password.
If it is working, on web pages with phone numbers you should see some modifications. Doesn't work for phone numbers in gmail though.