iCloud: Photo is locked due to account maintenance

I'm trying to upload photos (~50K of them) from my MacBook to iCloud. The process is quite glitchy - getting "aw shucks, your connection has broken" even though I am sending them in batches (~4k at a time).

Now I have been stopped, again, with the message Photo is locked due to account maintenance. Is it perhaps a mistake to be using iCloud for this many photos?

There's nothing wrong in uploading a large number of photos to your iCloud storage. You are only limited by the available storage space and not the count of photos that you upload in iCloud.

The error message appears due to some temporary issues in the iCloud backend, network connectivity issues or some minor system/maintenance issue.

When it happens, check the iCloud System status here:

• https://www.apple.com/ca/support/systemstatus/

To resolve the issue, retry after some time. If you are using a Web browser, try refreshing and reattempt upload.