A Microsoft file hosting and synchronization service.
I encountered this, today, on a newly created MS 365 user. They are on a Mac running macOS Big Sur, with MS Office and One Drive with mainstream updates as of November 2021 installed.
I opened a case with MS but while waiting for them to call me I logged the user in to their MS 365 account, online and opened their One Drive Web app. I was then able to log them in to their One Drive desktop app immediately.
The user had been created a good couple of hours prior to attempting to log them in to their One Drive desktop app but my guess is the provisioning systems on Microsoft's back end had nodded off and the act of logging in to their One Drive Web app woke the beast to complete provisioning the user's SharePoint services.