Why does philosophy.stackexchange suddenly label me as a new contributor when in fact I have already posted many questions in the last 2 years? It this related to deleting cookies from my pc?
You appear to have more than one account on that site.
While your other account indeed has many question, the account you used here has no old questions, just the one you posted today, so you're still considered a New Contributor.
Stack Exchange does not perform deep check for sock/alternative accounts, we're allowed to have them as long as they're not used in bad way, e.g. voting for each other.
You can ask to merge the accounts, this way no longer being New Contributor once they're merged, or leave it be.