The first thing to do when you receive a 500 error is restart your services - most times this will solve the problem! You can see posts on this forum tagged with a 500 error from the last couple of years here:
They all provide advice along the lines of the following:
If you haven't done this already, please see the following for some thoughts on troubleshooting and what kind of information to include if you need more help:
Additionally, when you encounter a 500 error, generally the first thing we recommend doing is having a systems administrator consult the webserver error logs. This will give you more specific information about the nature of the issue. See:
Generally, we recommend trying some of AtoM's common maintenance tasks - running these can resolve a lot of issues. For example, clearing the application cache, restarting services, etc. It's possible in your case that the job scheduler needs to be restarted. See:
If these resources don't help you solve the problem, let us know what version of AtoM you are running and how it is configured, what you find in the error logs and what happens if you try restarting services and repeating the steps, and we can go from there.