Mikel007 My friend had the same problem a few months ago where he was not able to create an account or even login with the existing account. Exact same problem.
After a lot of debugging I found that the problem was with his IP address. If the site does not like your Ip address it will give you endless troubles.
Even if your IP address is from your ISP, it could have been abused in the past by other users and because of that the IP would have been blacklisted.
Changing browsers in this scenario will not help.
You must get an IP address that the site thinks is clean (VPN is also fine).
You can google for this. Usually, FREE VPN and proxies would have been heavily abused in the past leading to them being blacklisted.
Once you get a clean IP address do not forget to clean your browser of all cookies, site-data, history etc. before starting a new session with the new IP address.
My friend ended up having to use a paid VPN to access the site without issues.