hi i heard someone over here on the mac roomers forms charges a small fee for cleaning people boot roms on the mac pro. im having a lot of issues with my mac pro and i think my pro needs a cleaned boot rom.
Please fully read this first post, you will probably find that you have one or more problems described into the various notes below. Mojave will only install if you have upgraded your BootROM to the current release and your Mac Pro have a Metal capable GPU*. If you are trying to install Mojave...
Also check the logic board battery the BR2032 is at least 3v many over look the battery when having issues. also make sure you replace with a BR2032 as the CR2032 will not last long if used as replacement.
You also don't say which Mac pro you have? Mac pro 4.1 flashed to 5.1 or a 2010 to 2012 genuine Mac pro 5.1. May even be a 3.1 you didn't mention which.