Hi,
On the overview page of the 'new' VM it will say what zone it is in. If your public IP is not zone specific then you may need to create a new public IP and either make it zone-redundant, or deploy to that specific zone that the VM is also deploy into in order to be able to associate it.
Once the new Public IP is created either as zone-redundant or in the particular zone that the VM is deployed in ( the new one) then you will be able to associate it (providing it's disassociated already).
See also a similar topic here: https://stackoverflow.com/questions/58189275/failed-to-save-ip-address-changes-for-network-interface
Any questions please comment and I'll try and help further if you need. If this answers your question then please mark it as accepted to help others.
Thanks