Best would be to get all the error codes read... It is very hard to say what is going on, without the help of VIDA.
Let the garage delete the codes, run the car for five to ten minutes around the block and readout the codes again. Let them printout the codes (all of them) and share that list here.
I don't understand what exactly they have done, during a software download is an error? Normally the new unit is connected to the car and afterwards the software will be installed (this is the part pairing the new unit and the car). That's it, if there is an error at that point it's Volvos problem. Your garage shouldn't need to install any other software.