up until 6.05.03 the Summoner spells class list is consistent with the APG.
beginning with 6.05.04 through to 6.06.00RC1/6.05.07 the Summon spells have been removed.
Not only does this prevent adding new Summon Monster X spells, but throws errors (no source) from existing characters being upgraded.
I note in the printed books that the Summon Monster series is different between APG & Pathfinder Unchained, and that Pathfinder Unchained is introduced in 6.05.04.
I have not loaded Unchained (it's not part of the Core books).
Even if I had loaded Unchained I would expect the Standard Summoner to be the default unless loading Pathfinder Society (I'm not).
Feats and Abilities> Class Features > Summoner Class Selection
has gained an option "Standard", which is not selected by default
However, even explicitly selecting it does not fix the Summon Monster spells.
Loading Pathfinder Core plus Pathfinder Unchained (Summoner Only)
makes the Class Selection offer Standard or Unchained summoner, but it still doesn't add the Summon Monster spells into the spell list to choose.
using Pathfinder RPG Core Supplements rule-set