Pages are loading and give error 504 gateway timeout

I am not able to see post and pages are consciously loading if we try to activate download manager plugin.

WordPress version :Current version: 6.4.3

plugin version : Version 3.2.89

we have around 1100 posts that not upload on our website and pages are continuous loading.

And we have got 504 error gateway timeout.

plugin setting we have chunk size 1024 kb chunk load option is disable

and download speed is 1096