A group of Microsoft Products and technologies used for sharing and managing content, knowledge, and applications.
Dear Lauren and Presley,
After involving some resources, there are on-going incident OD675907 and SP675906 "Some users may be unable to access OneDrive for Business content and get a '503' error" and "Some users may be unable to access SharePoint Online sites and get a '503' error" in SharePoint Online. The incidents has been investigated by our related team and based on the latest updates, they should have gone now.
I suggest you fully clear the browser cache, close the browser and log into OneDrive for Business and SharePoint Online with your account again to see if the issue goes away in your environments.
If the issue persists, I suggest you contact our related team so that they can help you fix the issues at their side directly.
As you are using a Microsoft 365 Business subscription, I suggest you contact the administrator in your company if you aren't the administrator and let him follow the steps in Get support - Microsoft 365 admin | Microsoft Learn to open a support ticket to our related team as soon as possible.
The administrator is always the first person who subscribes the Microsoft 365 business subscription or the IT administrator in your organization.
About admin roles in the Microsoft 365 admin center - Microsoft 365 admin | Microsoft Learn
How do I find my Microsoft 365 admin? - Microsoft Support
The administrator should be able to open the support ticket from Help & support in the Microsoft 365 admin center.
Then you can select the Phone support or the Email support as follows.
Thanks for your effort and hope that the issue can be soon resolved by our related team at your side.
Sincerely
Cliff | Microsoft Community Moderator