Short answer
A carrier-locked phone may block eSIM installation or connection, even if the phone supports eSIM.
What this means
The phone is restricted by your mobile carrier. Only that carrier can remove the lock.
What to do
Contact your carrier and ask whether the phone is unlocked for eSIM use.
If you already bought an eSIM and see a carrier-lock error, contact support with a screenshot of the exact error.
Important
We cannot remove a carrier lock from your phone.