I haven't used an esim before
I saw this comment
https://discuss.grapheneos.org/d/5863-esim-activation/24
From the same thread:
But resetting the Access Point Name menu populated it with the normal 2 EE entries, then I just had to select the radio button and boom, working.
Or this
Note that if the eSIM installation process does not progress past the "Checking network info..." stage despite having a stable Internet connection, you may need to call the USSD code ##4636## and then enable DSDS in the menu that is presented.
If you can't get it working even after other replies here, try contacting your carrier or getting a physical sim