EB2-to-EB3 downgrade; Approved I-140 from previous employer

[rivaldo 0]

Hi,

I had an approved I-140 (EB2) from my previous employer with priority date of Sept 2014. We had initiated the process in EB2 with my current employer but during pandemic documentation didn't reach USCIS in time and it got rejected despite a follow up request to USCIS.
Is the "downgrade to EB3" applicable to me ? If yes how much time does it take ?
OR
in order to switch to EB3 we'd just need to reinitiate the whole perm and I-140 process and file it in EB3 ?