Ok I've disabled a mod that might have been causing server connection issues and reset your world, just in case. I'm not sure if that solved it. Would you try getting a new ip by pressing the start server button, then try loading a simple mod like this one? https://mod.learntomod.com/badge_builders/2823?sequence=9054&position=0
If that didn't solve it, the next thing to try is this:
First, make sure your Minecraft username (aka Minecraft account name) is set correctly. To do that, go to the Account (gear) tab in the middle of the LearnToMod homepage and scroll down until you see MC name. Then login to your minecraft launcher and look in the upper left corner and you should see your Minecraft username. Now, go back to the LearnToMod website. You should still be on the Account (gear) page. Does your minecraft username match your MC name exactly? It is case-sensitive. It most likely shouldn't be an email.
Even if it is set correctly, click the blue 'change' link then type the correct Minecraft username.
When you're in world on minecraft, type /op YourMinecraftUsername into the chat area in Minecraft
Just replace YourMinecraftUsername with the real Minecraft username.