Custom add-in turn blank in outlook 2016

Runebk 1 Reputation point

Hi Community!

I'm having problems with my custom add-in for outlook. I usually install it from url manifest in the M365 admin center without any issues.

However I need to install the add-in on an OnPrem Exchange Server using Outlook 2016. I tried through the 365 admin center. The add-in is installed but don't show up in outlook.

I ended up installing it through Exchange Admin Center -> organisation -> add-in -> add from url. I got this error: "Value can not be null. Parameter name: constraintProvider"

I ended up downloading the mainfest og added the add-in from file. The add-in showed as it should in the toolbar and I thought we had solved the problem. However when we tried using the add-in, the task-pane/sidebar was completely blank. Nothing to show.

Can anyone help?

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