fatal error

I am getting a fatal error message on one of the forms on my site.
I have tried to revoke access, clicking the delete access key and then connected again and it will work for one or 2 submissions, then the message happens again. I found a similar post however, there was not solution listed. I would really appreciate your help.

Here is the message:

Fatal error: Uncaught exception ‘Google_IO_Exception’ with message ‘Problem with the SSL CA cert (path? access rights?)’ in /home2/robynb/public_html/wp-content/plugins/gmail-smtp/google-api-php-client/src/Google/IO/Curl.php:115 Stack trace: #0 /home2/robynb/public_html/wp-content/plugins/gmail-smtp/google-api-php-client/src/Google/IO/Abstract.php(136): Google_IO_Curl->executeRequest(Object(Google_Http_Request)) #1 /home2/robynb/public_html/wp-content/plugins/gmail-smtp/google-api-php-client/src/Google/Auth/OAuth2.php(342): Google_IO_Abstract->makeRequest(Object(Google_Http_Request)) #2 /home2/robynb/public_html/wp-content/plugins/gmail-smtp/google-api-php-client/src/Google/Auth/OAuth2.php(278): Google_Auth_OAuth2->refreshTokenRequest(Array) #3 /home2/robynb/public_html/wp-content/plugins/gmail-smtp/google-api-php-client/src/Google/Client.php(457): Google_Auth_OAuth2->refreshToken(‘1/vKtzBuoVHLgNk…’) #4 /home2/robynb/public_html/wp-content/plugins/gmail-smtp/class.phpmaileroauthgoogle.php(142): Google_Client->refreshTok in /home2/robynb/public_html/wp-content/plugins/gmail-smtp/google-api-php-client/src/Google/IO/Curl.php on line 115