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UNC Folder Path Appending File Name in folderPath Causing 400 Error

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Posted on by LM-17042025-0

Hi all,

I’m running into a persistent issue with a Power Automate flow that saves email attachments into a network-shared folder based on a UNC path.

📌 Goal:

Automatically save invoice attachments to a specific project folder using a UNC path pulled from an Excel lookup table.

🧩 Flow Summary:

Trigger: When a new email arrives (V3)

Get Attachment (V2)

Extract Project Number from attachment name

Look up UNC Root Folder Path from Excel table

Build the full folder path like:

\\US0531-PPFSS01\SHARED_PROJECTS\{ProjectNumber}\01_management\financial\client_inv

Use Create File to save the file with the original attachment name

🧨 Issue:

Despite setting folderPath correctly, Power Automate returns this error:

It seems like the file name is being appended to the folder path, treating the whole string as the folderPath, not separating folderPath from name.

✅ What I’ve already tried:

Verified Build File Path output is correct (confirmed with Compose)

File name is clean, confirmed via debug

Changed name from @items('Apply_to_each')?['Name'] to @outputs('Get_Attachment_(V2)')?['body/name']

Still getting the same 400 error referencing a full path that wrongly includes the file name

❓ What am I missing?

How do I ensure the Create File action only uses the intended folder path, and doesn’t interpret the full path + filename as folderPath?

Any help would be appreciated!

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Building flows

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Michael E. Gernaey 53,345 Super User 2025 Season 2 on at

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hi @LM-17042025-0

YOu will need to share your inputs into your Crreate File. Clearly you are creating a file for every attachment which is great and super easy, but you have so many filter array's and other actions that you are building up the wrong details to be used later on

We cannot tell that from the closed flow actions. What you need to do, is go through the flow run you have attached, open Each action, and see what input and ouputs it creates.

One of them is causing you to generate a path with the file name.

I know this to be true, because the Get Attachments action is not giving yuou a location in some share to use, so its your expressions doing it (aka a bug).

Walk it through slowly you will see it I promise

If this helps please Mark as such and maybe a like.

If you need more help please share all actions in the above run with inputs and outputs.

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LM-17042025-0 3 on at

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@Michael E. Gernaey I will attach screenshots. I don't want to create a new file for every attachment, i just want it to identify the project # based on the invoice name (taken from my email), then find the corresponding folder on one of 3 drives my company uses (aka if true use this drive, if false use this drive), and then save it in the correct folder, under invoices.

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