You upgraded to Symantec Endpoint Protection (SEP) 14.2 RU1 or higher on a Domino Server or a workstation or server running Lotus Notes.
After the upgrade, plugins such as IQ.Suite or Marvelclient stop working as expected.
This issue will be resolved in 14.3. Current ETA is early April 2020
Add the missing lines back to the notes.ini file.
For iQ.Suite add: ExtMgr_Addins=te_hook
For Marvelclient add: EXTMGR_ADDINS=mc.dll