Challenge with PW and Username

I have a bit of a challenge. I received a 6 month offer from a German site for a 6 month username and password. It worked for several days when I put it in and now it will not update in the mornings early updates. I wrote ESET and they were not that helpful. It then did start working later in the day but then now again it states that I have an invalid username etc.
I did copy/paste and and also manually placed the password in. As I said it did work and sometimes does work but it stops being valid each morning.
What is suggested for me to do at this point?
Thank you for any help.
KOR-

 

did you contact that German site maybe they can inquire with Eset?

 

Site is in German and I did just write them and hope they read English.

Thank you.
KOR-