Can you comment on this AWA? and give us some hints.
WebEqualizer, there is really very little I can say with any certainty, based on the minimal information here.
Honestly there could be many reasons, or, more likely, combinations of reasons, for 'getting only a few impressions', which seems to be the predominant theme here - but only a look at the accounts in question will pinpoint those reasons.
I review a huge number of advertiser emails daily in order to watch for issues which might be emerging, and I have not seen anything that hints at a system issue which would cause a reduction in impressions.
Almost certainly the causes are unique to the accounts. For this reason, I'd suggest contacting AdWords support by using the 'Contact Us' link within those accounts.
AWA