So my sales from April 27th till April 30th were not added to my overall earnings for April.

Now, I know it usually takes a day or two for the "Earnings" page to update, but it's been now 4 days and my earnings for April are still short for sales that I had in the last 4 days in April.

Is anyone having the same experience?

Mine has been going up daily.  I check every morning.

My sales total has not risen for a few days now. I seem to remember this happening last year and they corrected it in time for payout.

The same here.....

same here, but when I click your specific monthly earning (not overall) I can see correct amount but it is not added to my overall earnings

There stats rarely sync correctly across the site. This has been a problem there for years. You just have to wait for them to catch up.

Everyone thinks that there is a problem because not all sales reported in daily earning page are calculated in monthly earnings. How can we believe that all sales are reported in daily earning page? 

They also have not reviewed my last 4 batches - that's a backlog of more than a month.  They used to be a lot quicker.

Corrected

They also have not reviewed my last 4 batches - that's a backlog of more than a month.  They used to be a lot quicker.

Send them an email. It gets through very fast after that.