It was mandatory but essentially had to be done on your own time.

In the US, if you are an hourly non-exempt employee, that is overt wage theft in all 50 states. If a task is made mandatory by an employer, they must pay you for the time you spent on it.

I know this doesn’t help you now, of course, but it’s good to know in case you run into it again and feel like pushing back with a report to the Dept of Labor.