The Custom Form Cannot Be Opened. I've run into a similar problem when jumping back and forth between mine and customer tenants and various logins. Add the user with full control to the hkey_users registry key.
WhiteSmilingBullet_ Custom Form
Try creating a new profile in outlook and check. Go to “c:\users\%username%\appdata\local\microsoft\forms” then delete all items in the folder. To get things working right, i have to make to sign out of each microsoft service before signing into. Web in the forms manager box, click clear cache. To create a new profile in outlook refer: Web you should know that the form for emails is ipm.post, for calendar items is ipm.appointment. Check if microsoft outlook item uses a correct form. (please back up it before you delete it) check if the issue persists. Outlook will recreate this file when needed. If it doesn't work, you can try to manually clear the forms cache:
It can also be helpful to rename (or delete) frmcache.dat to frmcache.old. Go to “c:\users\%username%\appdata\local\microsoft\forms” then delete all items in the folder. Go to file menu >> options. Open outlook, click on the affected folder (contact folder), click properties, and change the default form to be used back to the standard form (ipm.contact). The form required to view this message cannot be displayed. this usually means the outlook forms cache is corrupted. Locate the folder where you want to create a new item; Outlook will recreate this file when needed. In the custom forms dialog box, click manage forms. To create a new profile in outlook refer: Outlook will use an outlook form instead. Go to the navigation pane;
