Please go to Dashboard > Front End PM > Settings > Recipient. Then untick “Can send to users” and tick “Can send to admin”. Add your admin username and Display as in that field and click “Save Changes”.

I have tested with this settings in my test and it is working perfectly. Can you please give me access to your website if it does not work? Please create 2 test user account ( 1 admin and another normal user ) and give credential to me.

Full backup your website before giving me access.