Entering the CLI command
installed-systems add <URL> generates an error and terminates the current SSH session to Management Center:
terminate called after throwing and instance of 'std;:runtime_error' what (): Negative integer can not be converted to unsigned integer "
These errors were reported on Management Center version 1.5.x and 1.4.x and prevent upgrading Management Center to a higher software version.
Rebooting Management Center does not help.
It was unknown how the Management Center goes into this state.
This issue was fixed in Management Center 184.108.40.206.
The only known workaround is to restore Management Center to factory defaults and do the upgrade.
Please see Management Center Configuration Management Guide.