A great thanks to Dravergy, as his Reddit post solved the issue.
If others are finding the same issue, the issue arises from the world generator
settings in the server's property file.
In simple terms:
1. Install a fresh copy of the Sevtech: Ages of the Sky Modpack, (It just helps with any errors)
Do not start the server yet! The world generation needs to be changed first!
2. Go to Files from the shortcut menu on the left of the screen on your main server page.
3. Go to server.properties
4. It should open up a few server settings, and scroll down to the one that says Generator.
5. Inside the box to the right of "Generator" put this in exactly, including the squiggly brackets!
5. Now boot the server!
6. Try it out now with your own client-side, or the modded Minecraft installed on your machine
7. It should now load correctly!!! IF THIS IS NOT THE CASE REFER BELOW
An issue that still may arise comes from the client side being rejected from the server as it requires a missing mod such as my case below:
BRING BACK BEDROCK REQUIRED
Sadly this is the case as the server pack has a bug where some mods that were removed are still required, so what you have to do is install it on your client-side. They won't be active however so they
shouldn't give any issues.
Essentially the simple fix is, find the missing mods jar file, which ya can get off Curseforge such as
BRING BACK BEDROCK
After doing so, add the jar file to your mod folder inside of your modded client.
If you don't know how to do this just do this
1. Open up the folder the Modpack is on your computer
( Curseforge lets you right-click on it and its in the drop down menu)
2. Go to the "mod" file
3. Drop the JAR File for the mod inside of it.
4. Boot it up and try again.
If there are any other errors, try to contact the Modpack dev team, they have more material and sources to reference for issues like this!!