iPhone 16 Merge Duplicate Contacts option disappeared

Hopefully somebody can help please.

I moved over from Android to Apple and as part of the process I suddenly have over a thousand contacts as there are several duplications.

I think the "Merge Contacts" option came up but I think I clicked "Ignore" as I wanted to do it later.

Now though the option to Merge Contacts has disappeared.

I know I can do them individually but this will take hours.

I have tried deleting from phone in iCloud settings and toggle back on but this hasn't worked

How do I get the Merge All option back?