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Error while deploying the Power Pages site to the UAT environment

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Posted on by omkarsupreme

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While deploying the Power Pages site to the UAT environment, I’m encountering the following error:

The attachment is either not a valid type or is too large. It cannot be uploaded or downloaded

While, I removed all file attachments from the solution and moved them to Blob Storage. After cleanup, the solution ZIP size is now only 990 KB, but the deployment is still failing with the same error.

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sumit_artesian 248 on at

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Hi @omkarsupreme,

This is a weird case of Power Pages. You get this error about invalid size, but it's almost always related to blocked file types in your target environment.

To fix this, follow these steps:

Navigate to Power Platform Admin Center.

Go to Manage -> Environments -> Select your UAT environment.

Go to Settings.

Expand Product and go to Privacy + Security.

Here, under Blocked Attachments, make sure you remove .js files as well as any other file type that is present in your solution, like .json, .config, .css, .html, .ts, and so on.

Once you allow these file types by removing them from the text box and saving your settings, try importing your solution again.

Please ✅ Does this answer your question if my post helped you solve your issue. This will help others find it more readily. It also closes the item.

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Valantis 5,197 on at

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Hi @omkarsupreme,

The error has nothing to do with file size since your ZIP is only 990 KB. The confirmed root cause is a blocked file extension in the UAT environment.

Power Pages solutions typically contain .js files (JavaScript for web pages, templates, etc.). Dataverse environments have a blocked file extensions list for attachments, and .js is blocked by default in many environments. When the solution tries to import those web files as Dataverse attachment records, the import fails with exactly this error.

Fix:

1. Go to the UAT environment's legacy settings: open the Dynamics 365 app in UAT, then Settings > Administration > System Settings > General tab
2. Find the field Blocked file extensions for attachments
3. Remove js from the list (and any other extension your Power Pages site uses, like .html or .css if they're also blocked)
4. Try the deployment again

After the deployment succeeds you can add .js back to the blocked list if your security policy requires it.

This is a confirmed fix documented by the Power Platform community and is the most common cause of this specific error during Power Pages solution imports regardless of the solution ZIP size.

Best regards,

Valantis

✅ If this helped solve your issue, please Accept as Solution so others can find it quickly.

❤️ If it didn’t fully solve it but was still useful, please click “Yes” on “Was this reply helpful?” or leave a Like :).

🏷️ For follow-ups @Valantis.

📝 https://valantisond365.com/

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