Did they replace the concentric slave cylinder at the same time ?, this needs to be 100% air free or you will have trouble.
Check also they have not bust plastic ends of the gear cables.
It is a pita job to do about 2-3 hours, cables are around £50 the pair(pattern) ZERO special tools needed, if the cables are a fault, I would check first it may just have air in the system.
Either way it went in selecting gears ?, it should do so coming back as well, some heavy handed monkeys manage to do the cables in though.
tabetha