Sophos Central Account Login doesn't work

Hello,

my Company upgraded from Sophos Endpoint Protection to Sophos Central Intercept X Advanced. Since years I've an old mySophos Account which was converted into a Sophos ID.

Logging in to the old Licencing Portal works well. To use Intercept X Advanced I need Sophos Central, but when I try to login to central.sophos.com I got the message "Authentication failed. Please check your credentials and try again".

When I try to create a new Central account I got the message "The email address n.hxxxn@fixxxxxxxton.de is already used for a Sophos account. "

I've also tried to reset my password, but it ends with the same result.

What could I do?

Regards