Not on 1st page = impression??

you DO get impressions if your ad is "not showing on the first page".

what's more, even with "your ad is not showing on the first page", you can still get first page impressions, and even get an average position that is clearly on page 1 - like 5.6 or 7.2

this is because the bidding auction is NOT the same every time - we all have different bids, geographies, daily budgets, show asap vs even spread, etc. which means sometimes, even with a low bid, you luck out and get a page 1 impression. we often use this strategy quite deliberately on high volume high price terms - bid 10% of the "first page min bid" and get a few hundred impressions per day - with really cheap clicks.

BUT the impression count is much lower, obviously (like 10% or less) than the possible impressions if you are bidding enough to get regular page 1.

also, if the URL is invalid, the AdVariant/keyword combo is generally inactive (even if it says it isn't) - i THINK that happens because the check is done the first time the AdVariant/keyword combo features in an auction, so until that first auction it claims it's ok.

if your ad is not showing at all:
1) check the URL is valid
2) crank up the bid price and budget, quickly run a few searches to spot the ad, then drop the bid and budget back again
3) if it still doesn't show, it may be manually blocked - e.g. if you have tripped a red flag and google's locked out the advariant until a human has checked it - wait 4-5 days and see if it restarts, then ask google support.

when searching for your ad, click the browser "refresh" a few times - notice how the ads displayed can change - yours might only come up every 3 or 4 refreshes.