I have read many pages of posts and have been unable to find a link to the official site for Acropolis tickets, other than a very recent post that gives a link for their new ticket site, but I didn’t see that it was actually available to purchase tickets for May. I would like to purchase early so we can get the first opening time of the day. Thanks in advance!
It is too early. Currently the portal is open for purchases up to March 31st. Usually the tickets for April 1st onwards opens up towards the end of March.
...other than a very recent post that provides a link to their new
ticket site
This post explains that you must wait until at least mid-March before you can purchase tickets starting April 1st, and that the new site is simply a redesigned homepage. The online ticket purchase section for the Acropolis is still accessible at the same web address:
https://hhticket.gr/tap_b2c_new/english/tap.exe?PM=P1P&place=000000002
You have plenty of time to get tickets for May.