Go into the ProxSpace environment, then run cd proxmark to change directory to where the proxmark files should be located, then git pull to pull the latest release, then make clean && make all to compile, ./pm3-flash-bootrom to flash the bootrom, and finally ./pm3-flash-fullimage to flash the full image.
Pulling this from:
The only difference is you already have the files from the Proxmark GitHub, so you want to do git pull instead of git clone to update the files.
And I changed make clean && make -j8 all because iirc that was messing with some people. The -j8 tells it to run multiple threads during compiling which should make it faster but taking that out doesn’t hurt the process.