VSTO excel plugin designed is not visible or collapsed only for excel 365 when loaded, but for other excel version like 2016/19 etc it works as designed.

Question

We have an excel VSTO addin as one of our products, it is working as designed in visual studio as expected for all excel version apart from Excel 365.
Does this is related to any setting in excel or visual studio, do we require to re-engineer UI again? kindly suggest applicable.

Same question I have asked in office support site, I was suggested to ask question here, so following it, link of office question is bellow,
https://answers.microsoft.com/en-us/msoffice/forum/all/vsto-excel-plugin-user-interface-is-not-shown/aea6d58e-e83e-47ce-956f-d206456a1f44

Deformed UI in Excel 365 looks like bellow,

Answer 1

Hello there,

Try adding the VSTO_SUPPRESSDISPLAYALERTS environment variable (set to 0).
Check if the add-in had been hard disabled by Office 365. Re-enable a hard disabled add-in by following the below steps

In the Manage box, change COM Add-ins to Disabled Add-ins, and then click Go.
Select the add-in and click Enable. Click Close.

Now the add-in can be loaded again:

In the Manage box, change Disabled Add-ins to COM Add-ins, and then click Go.
select the check box next to the disabled add-in. Click OK.

I hope this information helps. If you have any questions please let me know and I will be glad to help you out.

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