This is normal on a fresh install. The placeholder snapshot contains zero profiles until an approved snapshot is downloaded.
Pass the WoW installation path to the installer or check that the addon is already installed under _retail_/Interface/AddOns/MPlusForm.
Start World of Warcraft once with MPlusForm enabled, then log out or reload UI so the SavedVariables file is written.
Make sure combat logging is enabled during a Mythic+ run. The sync client expects a configured WoWCombatLog.txt path.
Check the configured server URL, local network access, and sync logs. The addon can still run with the last available snapshot.
Use:
/mpf tooltip off
To enable it again:
/mpf tooltip on