“A form region cannot be opened” is an error related to Outlook and Skype for Business (or Lync).
Normally, Skype for Business conversations will be linked and saved in Conversation History in Outlook. You want to review chat history, you just go to this item and see it directly on the right hand side of Outlook. However, the error has occurred, you cannot view live view and  see the following error message:

“A form region cannot be opened”

Some error messages are similar to the following:


The cause of all the above errors is the Add-in - Conversation History on Outlook.

 
How to do:

Fix "A form region cannot be opened" error

Step 1: Open Outlook > File > Options > Add-Ins



Step 2: In the Add-Ins panel, find out whether there is Conversation History Add-Ins for Microsoft Office? If so, please go to Step 3



Step 3: Click Go… > Uncheck the Conversation History Add-Ins for Microsoft Office as below.
When you uncheck it, this Add-Ins will inactive in Outlook. 



Step 4: Click OK to agree.


Step 5: Go back to the Add-Ins panel just then, check if Conversation History Add-Ins for Microsoft Office has been inactive.

OK, Done. Now you open Outlook again and check again

Conclusion:
This method is 100% successful, helping you to fix the error "A form region cannot be opened" on Conversation History Outlook. If you have any questions, please comment below. Thank you everyone!

Tags:

A form region cannot be opened, Outlook, Skype for Business , Conversation History, Conversation History Add-Ins for Microsoft Office, Conversation History Add-Ins