You have already seen that in affirmative sentences with depuis (= I have done this since/for + [date/duration]), you must use Présent indicatif in French, unlike the English Present Perfect.
See lesson Using 'depuis' (since / for) with Le Présent and NOT Le Passé Composé (prepositions of time)
But things change when it comes to negative statements (ne...pas) with depuis.
Indeed, in such cases, you will actually use Passé composé in French, as such:
Here we use Passé composé because the use of the negation ne ... pas insists on the fact that the action stopped happening at the specific time mentioned (since/for) in the past.
If we used Présent indicatif here, it would make it sound like the action "keeps on stopping" during the given length of time.
To say that a (recurring) action in the past has now stopped happening with depuis, you can also use Présent indicatif with ne ... plus (not any more) instead of ne ... pas:
Special case of depuis longtemps = not long vs not in a long time
Ne...plus + Présent indicatif + depuis longtemps
= not for a long time / not in ages
-> It's over and done in the past
-> It started a short while ago, and is still ongoing