I have added my gmail account to Apple mail and followed the directions for doing so. It continues to have the offline symbol next to the inbox and won't load my mail.

Let's start with double-checking to see if your Gmail account is working properly.

Please try the following:

1. Using a web browser, see if you can successfully log on to your Gmail account and access your messages there. If you can, go on to the next step.
2. Use the Apple Connection Doctor. Ref: Use Connection Doctor in Mail on Mac - Apple Support

Please post back with your results.