If you want assistance from the Community Forum then you'll need to explain/describe your issue more clearly and in more detail.
What exactly do you mean by "activate my membership" and "is not working"?
Monthly membership plans don't need activation, they just start automatically.
What exactly do you mean by "I tried to activate my membership"?
What exactly did you do?
What exactly isn't working?
When was everything working ok last?
What changed in the meantime?
When were you last able to successfully buy and use a monthly membership plan?
If you need to contact 48 support about this then see the links in my signature below.
