Can't seem to open an ISA

I already hold stocks with freetrade and therefore the app doesn’t seem to allow me to open an ISA. Can I not hold a “nominee account” and ISA at the same time? Must I sell all my stocks and then “bed and isa”?

Alex’s post I think should clear this up.

Essentially ISAs are in an early implementation phase so you can only hold one account, ISA or GIA (general investing account) for the time being, not both. That will likely change in the next few months though when ISAs roll out fully.