The "active but zero spend" issue has indeed popped up for many advertisers recently, even those with seasoned accounts. It's like Meta is just deciding not to deliver, even when everything looks good.
Here's what you should check and try, based on common fixes for this specific problem:
Double-Check All the Basics (Again!):
Ad Statuses: Go all the way down to the individual ad level. Make sure every single ad is "Active" and not "Processing," "In Review," "Learning Limited," or "Rejected." Even one ad stuck can hold up the whole ad set/campaign.
Ad Set Status: Ensure the ad set is "Active."
Campaign Status: Confirm the campaign is "Active."
Budget: Is your daily/lifetime budget sufficient? Sometimes if it's too low, especially for the audience size or bidding strategy, it won't spend.
Audience Size: Is your audience accidentally too narrow? Duplicating can sometimes mess with exclusions or combined audiences.
Payment Method: Even if you think it's fine, check "Billing & Payment Methods" in your Ad Account settings for any warnings, failed charges, or spend limits reached. This is a very common culprit for zero spend.
Ad Account Limits: See if your ad account has any daily or lifetime spend limits that might have been hit.
The "Processing" Hang-Up: You mentioned it sat in processing for hours. This is often the root cause. Even if it says "Active" now, something might have glitched during that initial review/processing.
Try the "Duplicate an Ad" Trick (Even if the campaign is active):
Go into your problematic ad set.
Select just one of the ads within it.
Click "Duplicate Ad" (choose "Existing Campaign" and put it into the same ad set).
Publish this single duplicated ad.
Often, this forces a fresh review and can kickstart delivery for the entire ad set.
Create a Brand New Ad Set (with the same ads):
If the single ad duplication doesn't work, try duplicating the entire ad set within the existing campaign.
Keep all the settings (targeting, creative, budget) exactly the same.
Publish the new ad set. This creates completely new ad IDs and usually forces the system to re-evaluate and deliver.
Small Budget Increase (Test): Sometimes a tiny nudge in the budget (e.g., from $10 to $11) can kick a campaign out of a limbo state, especially if it's stuck in a competitive auction.
Contact Meta Support: If none of the above work after giving them a few hours each, you'll need to reach out to Meta Support directly.
Be persistent. Explain exactly what you've done, the status of your campaign, and that it's zero spend despite being active. Provide screenshots.
Use the live chat option if available (often found in the Business Help Center if your account qualifies).
This situation is incredibly annoying because the system says it's working, but it's not. It's almost always an invisible glitch or a subtle hold-up in their internal delivery system. Good luck!