Short answer
This usually means the phone does not support eSIM, the regional model does not support eSIM, or the phone is carrier-locked.
Check first
Look for Add eSIM / Add Cellular Plan in phone settings.
Dial *#06# and check whether an EID appears.
Check whether the phone is unlocked.
Important
Some phone models support eSIM in one country/region but not another. A successful purchase cannot make an unsupported device compatible.
If the phone is unsupported or carrier-locked
The eSIM may not install on that device. Contact support if you need a review and send a screenshot of the error.