When trying to perform a mass erase of the chip, you get an error, e.g. UMI error. For mass erase to work, the CPU should be stopped. In case you have a multi-core device, the non-primary cores should be stopped as well.
Enable this option via the Hardware menu / <device> / Configure Device
Open View menu / Debug / Session Explorer and check status of CPU cores.
Sorry this article didn't answer your question, we'd love to hear how we can improve it.
Note: This form won't submit a case. We'll just use it to make this article better.