Archfiend Coffer

[DrWho2010]

you *should* be able to spend trophy crystals to get Series 1 rewards until the start of Series 3 (even if you didn't reach that level in Series 1). check the vendor tomorrow after the servers come back up.

[Nezerius]

you *should* be able to spend trophy crystals to get Series 1 rewards until the start of Series 3 (even if you didn't reach that level in Series 1). check the vendor tomorrow after the servers come back up.

They've been incredibly vague when it comes to this.
Unofficial translation had a line where Yoshi-P stated "If you didn't make it in time, you can still use these crystals to obtain the rewards for the previous series, they will stay for one additional patch but will be gone after that"
Official digest of the same live letter simply states "With each Series, your Series Level will be reset and the reward lineup will be changed, but you’ll be able to obtain rewards from one Series prior."
Patch notes, and a separate lodestone post about Series 1 ending simply state that rewards can only be claimed until the end of Series 2.

So yea, OP, best bet is to just hope for the best and check the PvP vendor after maintenance.