1. If there are clear spam posts, report them. Save their links so you can track whether the mods respond. You may find here that they're not inactive after all, in which case the problem is solved.
2. Reach out to the mods, in a post asking to be added to the mod team. Again, save the url to track whether the mods respond. You may find here that they're willing to accept help and add you as a mod, again problem solved.
3. If reaching out to the mods as described above fails, you need admin help. Post in [email protected] or email [email protected] with the results of 1 and 2, along with any violations of the moderators guide pinned in the moderators community.

The admins generally won't intervene until you've made a good faith attempt to coordinate directly with the mods and documented a clear case that they're unresponsive or malicious.