demo version

Put the summary of the bug you're having here
i was on the mineplex server, they asked to download a resource pack so i clicked the link and the game crashed, now every time i want to start minecraft i can only play the demo version. i have tried to log in on all possible e-mail adresses and tried all kinds of passwords but i won't work, i have also changed my passwords and nothing works, i already linked it to mojang so i dont know what the problem is .

What I expected to happen was...:
Describe what you thought should happen here
i wanted to start minecraft
What actually happened was...:
Describe what happened here
it said i could only play the demo version
Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...
3. ...