Error 526 when uploading MP4 to LinkedIn and Pabbly Upload File

Hello,

We are experiencing a persistent Error 526 when Pabbly Connect tries to process an MP4 file.

The issue occurs in two places:

1. When publishing a video to LinkedIn through Pabbly Connect.
2. When using the Pabbly "Upload File" action with the same MP4 URL.

Example MP4 URL:

https://api.m4w.pl/ugc/4.mp4

We have thoroughly tested the file and our hosting server.

The file is publicly accessible and returns the correct HTTP headers:

• HEAD request: HTTP 200 OK
• Content-Type: video/mp4
• Content-Length: 2,824,659 bytes
• Accept-Ranges: bytes
• HTTPS/SSL works correctly

We also tested a Range request:

• GET with Range: bytes=0-1023
• Server correctly returns HTTP 206 Partial Content
• Correct Content-Range header is returned

The important part is that our hosting provider checked the server logs for the exact time when Pabbly returned Error 526. They confirmed that there was no incoming connection or request to api.m4w.pl at that time.

This suggests that the error occurs on the Pabbly side before Pabbly actually attempts to connect to or download the MP4 file from our server.

The same URL works correctly when accessed directly and when downloaded using cURL.

Could you please check the Pabbly-side logs for this request and verify why Error 526 is being generated before any connection reaches our server?

This is currently preventing us from publishing MP4 videos to LinkedIn through our workflow.

Thank you.

Hello there,

Thanks for contacting us.

Could you please share the Workflow URL so that we can look into it and provide information accordingly?

Please be aware that to assist you effectively, we may need to access your Pabbly Connect account. If you're comfortable with this, please grant us permission by stating in your next email: "You have my permission to log into my Pabbly Connect account, and edit workflow {If required}. Here is the registered email address associated with it."

https://connect.pabbly.com/workflow/mapping/IjU3NjYwNTZjMDYzMDA0MzQ1MjZjNTUzYzUxM2Ii_pc

Hello,

I already provided the Workflow URL and granted permission for your support team to access my Pabbly Connect account when I created this thread.

Are you unable to see the information and permissions that I provided when submitting the original post?

Please let me know if I need to provide them again here in the reply.

Thank you.

Hello there,

After reviewing the workflow, I've escalated the issue to the Technical Team for further investigation. We will get back to you as soon as we hear from the Team. It may take up to 48 hours to get back to you.

We regret the inconvenience caused to you.

Hello Łukasz,

Thank you for your patience while our technical team investigated this issue.

Our engineering team checked the backend logs for your workflow and identified the root cause of the Error 526:

• Root Cause: The SSL certificate configuration on your file server (api.m4w.pl) is non-standard. Because of this non-standard setup, our downloader service cannot successfully verify the SSL certificate handshake, which triggers the 526 error prior to downloading.

• Verification Test: To confirm this, we tested uploading the exact same video file via a standard CDN (Google Drive) into the Upload File action, and the step executed successfully without any errors.

Workaround & Next Steps: To resolve this immediately and allow your workflows to run, please host your video files on a standard media hosting service or CDN—such as Amazon S3, Google Drive, Dropbox, or a standard public CDN—and use that public URL in your Pabbly Connect workflow steps.

Please let us know if you need any assistance updating your workflow!

I trust you’re doing well. I wanted to check in regarding the email I sent earlier.

Hello there,

I hope this message finds you well. I’m following up on my previous email. Further, this is our last follow-up email. The ticket will be closed automatically as we have not received a reply. You can email us again at support@pabbly.com to raise any new concerns.