You need to go back a step and choose "do something else" to get to the partition listing, find the efi partition and right-click, select 'change'.
I forget the exact wording, but in the dialogue that pops up there will be a "use as" option select, choose efi, and accept changes. You should also make sure / and swap partitions are set correctly ("use as" / or swap respectively).
Then continue with the installation.
Worked for me, seems the installer can miss the partition for some reason.
I encountered this recently myself.
You need to go back a step and choose "do something else" to get to the partition listing, find the efi partition and right-click, select 'change'.
I forget the exact wording, but in the dialogue that pops up there will be a "use as" option select, choose efi, and accept changes. You should also make sure / and swap partitions are set correctly ("use as" / or swap respectively).
Then continue with the installation.
Worked for me, seems the installer can miss the partition for some reason.