Unable to upload large video files

I have a large video file (226mb .mp4) that I am trying to upload to my site. I keep getting the following message:

Error

ā€˜The file could not be uploadedā€™

Iā€™ve chatted extensively with my server host and have made the necessary adjustments to my server with generous increases to memory_limit, max_execution_time, post_max_size, upload_max_filesize, max_input_vars

Iā€™ve trawled through numerous threads in the forum relating to video upload issues looking for an answer but I havenā€™t found a solution.

My host suggested it might be Cloudflare related, but I have tried uploading with the proxy disabled an d still encounter the same issue.

I get this message in the console after a failure to upload:

{"status":"error","message":"Unauthenticated","code":403,"key":"error.permission","details":[]}

It appears to originate from:

/api//pages/PAGE/fields/video/upload

Does anyone have any insight into what I could try next?

Many thanks.

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Make sure that your memory etc settings are really supported by the server, it doesnā€™t help if you set these values up high if the hosting doesnā€™t support it. Like often, for example max_execution_time is limited and uploading huge files might take longer.

Thanks @texnixe.

Iā€™ve had an engineer at the hosting company set the maximum values across the board. Varnish is also disabled.

Unfortunately, none of this has worked so it looks like Iā€™m going to have to embed iframes.