Due to a problem in the Intel® Quartus® Prime Pro Edition Software, you may see this internal error if your .qsf (quartus settings file) contains the following assignment:
set_global_assignment -name ENABLE_UNUSED_RX_CLOCK_WORKAROUND ON
To avoid this error, remove the assignment as it is no longer supported.
To preserve any unused transceiver rx channels in your design, use the following assignment instead:
set_instance_assignment -name PRESERVE_UNUSED_XCVR_CHANNEL ON -to <pin_name>
This problem is scheduled to be fixed in a future release of the Intel® Quartus® Prime Pro Edition Software.