Sorry for your lack of success

First MM status has no impact on upgrades.

RPUs place you ahead of CPUs.

But ahead of you are all GS (even GS using CPU) and all elites on Y or B fares that have not been Instant Upgraded.
Additionally all 1K on M fares or requested RPUs on higher fares than you.
Depending on the route and day, these can be a significant number of folks.

Additionally at check-in -- do you allow the system to split your PNR (if booked together)? If not you will not be considered for upgrading at the gate.

see the prioritization process at Upgrades Overview

On a personal note, I'm nearly 100% on use of RPUs but the few cases it has not worked is when the RPU did not clear at booking or before the start of the CPU window.