Hello, jepink.
Welcome to Apple Support Communities.
I understand that you're unable to send or receive your Gmail using the Apple Mail App. I may be able to help with this. Do you recall how you set up the Gmail account? Here's a great link to start:
If you can’t send or receive email on your Mac
If your Mac is connected to the Internet, but Mail no longer sends or receives email messages, the issue could be with the provider of your email service. Or you could have missing or outdated settings in the Accounts section of Mail preferences (Mail > Preferences).
This article may help narrow down what the exact issue is, check it out:
Use Mail Connection Doctor
If you're connected to the Internet but Mail Connection Doctor shows a red dot next to one or more of your accounts, check the Details column for messages such as the following:
Your email service may be experiencing a service outage. Contact them or use their status webpage to make sure that their mail service is online. You may also get this message if the password for your account is missing or no longer valid.
The settings for your email account may not be correct. Check Mail preferences to make sure that your email account settings are up to date. You can use the Mail Settings Lookup tool to check the settings for many email providers, or get them from your email provider.
You may also see this message if a network firewall is blocking the connection to your email service. That can happen if you installed third-party firewall software, or you're on a different network that doesn't allow the necessary email connections. If you're connecting from your corporate network, contact your corporate IT department for help. If you're connecting from somewhere else, such as a coffee shop or Internet cafe, check with their staff.
Let me know if this helps.
Thank you for using Apple Support Communities.
Cheers!
