Grunion Plugin – does not accept valid email address

Hello, I just installed the Grunion plugin to set up a contact form on a website. So far I have tested the form successfully twice with two different email addresses, but most of the time it rejects email addresses even when they are valid. After entering a valid email address and hitting “submit” I get this error message:

Email requires a valid email address

I searched the forum for discussions on this issue, but could not find any info. I figure it must have something to do with the code that’s validating the email input field.

Has anyone encountered this problem? Any help or insight would be appreciated.

Thanks in advance.