Question: Lower level button on one station is not latching. Top side is latching. Checked software, non-latching is not set on this station or specific key label. Any ideas?
Answer:  Here are several areas to check if the problem is software, hardware or configuration related:
1.)  Look at the Matrix +3 software and verify that the label with the issue hasn't been set to be Latch Disabled in the Configure / Global Advanced screen and in the Configure / Local Advanced screen.
2.)  Another quick test would be to swap the non-latching key on the lower row of keys to another key on the lower row and see if the issue stays with the label name or the key position. If it stays with the key position the issue might be a defective key latching mechanism on the panel.
3.)  Sometimes the frame and or configuration can be the issue, reset the frame either by performing a manual reset of the config-1 card or the individual MTX / MVX cards or by simply power cycling the frame. Reload the configuration file if need be and see if this cures the non-latching key condition. 
4.)  Open the diagnostics section of PGM-WIN and check the on-line status of the affected panel and also check that the firmware versions embedded in the frame cards (config-1 and all MTX / MVX) and connected panels matches the software used to make changes to the system. Mismatched software / firmware can be the biggest issue in proper system operation of a Matrix +3 system. Run the firmware version report to determine if all components have the same firmware version and that it matches the same software version used.