Hi, I'm John!
After purchasing additional storage (or freeing space), it can take up to 24 to 48 hours for everything to fully update across your account. I’d recommend waiting that time and then trying again to check emails or try to send.
If the update is still pending after 24 hours, you can try unlinking and relinking your OneDrive account, or resetting it. "Unlink and re-link OneDrive" https://support.microsoft.com/office/unlink-and-re-link-onedrive-3c4680bf-cc36-4204-9ca5-e7b24cdd23ea
If you're using Outlook Web, you can try resetting your browser cache and cookies. You can also try another browser, or test in incognito or InPrivate mode.
If the issue still persists, please wait another 24 hours for everything to fully update across your account.
I really hope this information is helpful! Let me know if you have any further questions or concerns.
Regards,
John J.D.