22 December 2021
If you open the server properties and the information you have filled out is there after you start the server, then AMP is doing its job correctly.
Did you check the Minecraft logs? There may be something in there that can help you further. It may be the case that the URL you are using for the resource pack is not a valid one - in other words, it needs to be a DIRECT download link to a file hosted somewhere, not a redirect.
Oh and, historically, there has been a maximum size limit for resource packs on servers. I am not sure what it is now, but sources say it used to be 50 MB.