The firmware question can be determined by connecting it to a computer with a serial cable and using the Topcon Receiver Utility [TRU] software to ascertain the firmware version by clicking on the Information icon in the main menu under “Receiver Management.”
if the firmware is dated before the beginning of 2019, it needs the update. A word of warning: older receiver sometimes begin to give a “board health” warning after new firmware is loaded. I have a pair of GR-3 receivers that happened to when I loaded the GPS week rollover firmware update on them. They still work, but they are a little slower to initialize that they were before loading the new firmware.
Since you mention a single receiver, I presume you must have been using to collect observations for OPUS submissions. If it does not have that firmware update from early 2019, the receiver misinterprets the GPS date and puts a date from almost 20 years ago on the file. OPUS will not process that file unless you know how to tinker with the RINEX data to correct the dates.