Devices stopped to receive uplinks after v3 migration

Just please make it clear for me:
How to Migrate Gateways from V2 to V3 - here is the advice to not migrate gateways to v3
How to Migrate Gateways from V2 to V3 - #10 by Jeff-UK - here is the advice to not delete gateways because of further problems with re-creating them

But I also used your advice to create v3 gateways (same as in v2) - status disconnected on all of them and no data received.- according above warnings, should I delete v2 gateways, or what is the correct step there?