I can't connect when I put my dbmovies API

[+ valerospora]

Hello! 
I have purchased a license, activated my account, logged in at https://dbmvs.com/, then I get my API key, and when I finally enter it in my wordpress and save changes, it is blank, I had to close and open again but I request the API key again.

I have uninstalled the plugins and nothing happens, the same error occurs, I suspect that is the issue, I need help, thanks.

[+ leen12]

could be some php setting or required  extension that is not installed