Here's an article that has screencaps: https://learntomod.freshdesk.com/support/solutions/articles/12000010794-setting-your-minecraft-username-on-learntomod
Basically, I want to make sure that your minecraft username (as seen on the learntomod website) matches the username on the minecraft launcher you're using right now exactly.
After checking that the username matches, the next thing is to make sure you're not opped out in Minecraft.
One way to do that is to use the command square on the server admin page to run op YourMinecraftUsername
You can also try typing /op YourMinecraftUsername into the chat area in Minecraft after entering your world.
Just replace YourMinecraftUsername with the real Minecraft username.
If that doesn't solve it, please let me know any error messages that you're seeing or send screenshots of what happens when mods fail to load, so I can investigate further. It would also help if you started a new forum post with that info.
To take screenshots in minecraft, press f2 or fn and f2 on your keyboard then look in your computer's minecraft < screenshots folder.