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Power Automate keeps flagging my condition as having “invalid expressions”

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Posted on by LD-08011232-0

Hi everyone,

I was asked to start a project to automatically reply to customer emails for our organization. I have little to no experience with programming or Power Automate, but after a lot of testing I managed to build a flow. The basic version worked correctly. It contained a Run a Prompt, but I removed this for testing purposes. My next step was to exclude certain senders and subject lines using conditions. I can save the draft, but when I try to test or publish, I consistently get this error:

Translated: The inputs of the action Doorgestuurd_of_reactie contain one or more invalid expressions. Please correct the invalid expressions for the inputs of this action.

What I’ve tried:

Rebuilt the entire flow from scratch to avoid possible old dynamic values.
Followed Copilot tips.
Ran Flow checker (no errors reported).
Removed the first condition; then the same error appears on the next condition.
Swapped in different dynamic values; same result. On the screenshot I didn't change it back yet.

I searched online but couldn’t find a solution. Does anyone know what I need to change to get past this error?

Thank you in advance for you advice!

Kind regards,

Laurens

PS: I’m in the new designer mode and can’t exit it until I publish the draft—but publishing is blocked by the error, so I can’t switch to Code view to edit the expressions there.

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Building flows

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David_MA 14,761 Super User 2026 Season 1 on at

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This may not be the issue, but for the third criteria in the condition, it is blank. That may be the issue. Try deleting that to see if it resolves the problem:

If that empty condition is supposed to do something, please explain what you are attempting to do with an empty condition. I also see that you have the From value in the condition to check if it starts with RE: or FW:. I believe you may want check this for the e-mail subject instead.

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LD-08011232-0 2 on at

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I did think that could be an issue, but the problem is that I can't remove the empty criteria. I work in the online environment of Power Automate, and when I start to fill an empty criteria, a new one pops up. I can't remove the empty one. In the screenshot, you can see that there is a possibility to delete it, but it doesn't work. Nothing happens when I press it for the empty criteria. When I do this for the test criteria, it works, but I still have an empty criteria left.

So I think this is a design feature?

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JL-09010807-0 2 on at

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"The last condition is blank" is not the issue. I also encounter this issue, when I add a new criteria, it will show a new blank below automatically and can not be deleted.

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David_MA 14,761 Super User 2026 Season 1 on at

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What does Copilot tell you when you click on the Assist me button in the error message?

I rarely use the new designer, but the old designer doesn't show a blank condition when you add a condition:

When I switch to the new designer, it doesn't show a blank row either:

I still think this may be the issue.

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IA-13011318-0 2 on at

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I rebuilt my flow in the old version and now it works. So that was the issue. Thanks for your help!

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