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Unpaid? I guess I missed where we have to pay for images we uploaded years before.
You probably just never uploaded enough per day to run into the upload fees. They start at 250 MB per day, see FAQ.
Am I understanding that our profile pics were deleted because now they cost credits?
No, they are still free and were marked as such in the database before the migration. When we checked if an image was paid, we always checked first if it was free, in which case it was considered paid.
After the migration, this intricacy led to these free images being considered unpaid as far as our background process to delete unpaid images was concerned.