If you can't access google mail account on the computer. it means, something is wrong with the user account or password. so here are the guide to fix it on your device.
First of all, you need to reset the google mail password now setup the new password on account.
Make sure that the Gmail services are running fine without any error.
Sometimes, Gmail is not working because of the mail settings or account settings issue.
Let's update the browser and mail application. it should be working fine without any error.