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Level 8

Start an approval failing with "500 bad gateway"

I have a flow where a variable is initialised with two email address in our organisation, separated with semicolons, and then further emails are added to the variable, again separated with semicolons.


This variable is then used as the list of approvers to send to.


However each time the flow runs the "Start an Approval" task fails with the error: 
InternalServerError. The request failed. Error code: '500'. Error Message: 'BadGateway'.

This messages does not tell me anything useful, so I am unsure as to what the problem is.

Here is my flow:




And here is the "Start and approval" task in edit mode:



What could the problem be?

Thanks for any help,


Community Support Team
Community Support Team

Re: Start an approval failing with "500 bad gateway"

Hi @rmmcgr,


If the error code 500 appears, the failure is temporary or transient. Click or tap Resubmit to try the flow again.

Also please take a try to delete the dynamic conteent in the "Start an approval" action to see if the issue still exists.


Best regards,



Re: Start an approval failing with "500 bad gateway"

Hello,  @rmmcgr!

Have you had an opportunity to apply @v-yuazh-msft‘s recommendation to adapt your Flow? If yes, and you find that solution to be satisfactory, please go ahead and click “Accept as Solution” so that this thread will be marked for other users to easily identify!

Thank you for being an active member of the Flow Community!

Flow Community Manager

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Level 8

Re: Start an approval failing with "500 bad gateway"

I did try the recommendation but unfortunately it did not work.


I have raised a support ticket and will see what happens from there.




Re: Start an approval failing with "500 bad gateway"

Did you get any resolution on this issue? I'm running into the same thing

Level: Powered On

Re: Start an approval failing with "500 bad gateway"

I have the same issue and tried many ways but all failed. Anyone has solution? Thanks.
Level 8

Re: Start an approval failing with "500 bad gateway"

So it turns out the problem in our case was related to the fact that we were using some an email addresses that were  distribution groups/Office 365 groups.


I think the approval flows will only work with approval requests to emails associated with proper user accounts in Office 365. Once we removed the group email addresses it started working.


Hope this helps,


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