We were in Paris recently and had a bad experience with the Paris Museum Pass and the Louvre Museum. The pass indicates that it gives access to the Louvre.
On Friday July 19th, we tried to use it around 5 PM and were told that the museum had stopped accepting it around 3 PM that day. We were told to buy timed tickets online. Unfortunately, all of the timed tickets were sold out through Wednesday the 24th, and we were leaving on the 23rd. We got in line for the Louvre before 9 AM on Sunday and Monday. Each day around 9:45 a Louvre employee told us that they were no longer admitting Paris Museum Pass holders because the Museum was "Full".
The Paris Museum Pass website does not provide any way to contact the company or apply for a refund.
If you want to see the Louvre, do not rely on the Paris Museum Pass. The museum will not honor it.