Please try this: Using Windows Explorer, go to this folder:

C:\Users\<username>\AppData\Local\Conceiva\Mezzmo

(where <username> is your Windows username. If you cannot find this folder, then search for "Mezzmo.db" on your computer and you should find the correct folder this way.)

Rename the 'Mezzmo' folder to '_Mezzmo'. This will make Mezzmo start from a fresh database, in case anything is corrupted in your current Mezzmo database. Run Mezzmo now. Does it start up OK?

If Mezzmo did not start up OK, then try this: Using Windows Explorer, go to the Mezzmo program folder and rename the 'CER.DLL' file to '_CER.DLL'. Run Mezzmo now. Does it start up OK?

Let me know how you go.