The plot thickens!
AGM’s need to be held within one month either side of the date that the Plan’s first ever such Meeting was held, so yours probably has some leeway in terms of its date.
Notwithstanding any delegations to your Strata Manager, it’s your Executive Committee Secretary who has the ultimate authority to convene General Meetings, so in the circumstances where there are numerous addenda and it’s likely that some Owners without email would not have received the most recent of those within the prescribed timeframe, it’s entirely appropriate for the Secretary to advise your Strata Manager that the AGM is postponed until such time as a consolidated and properly formed Agenda is available for re-issue.
I can’t help wondering how your new Strata Manager is so unaware of the requirements of Sch. 2 of the SCMA!