I had a simillar problem until 2 days ago - the blower would work only on high speed or not at all.
The problem is with the blower which is broken but also, you will have to change the thermoresistence which is attached to the blower.
They are sold separately but I advise you to buy both. The blower is located behind the lower glovebox.
You will have to go to a good mechanic because you must remove the dashboard.
The lower glovebox is embedded in the dashboard and there is no room to remove the blower unless you remove the dashboard.
They should cost both aprox 200 euro plus the work of installing the new blower.