If you have unlocked every ichor unlock category but one AND are playing with a controller AND you select it, then back out of it, THEN you cannot reselect it. I assume the UI expects you to use your dpad to select a different one to offer the confirm prompt, but since there are no other options, you cannot perform any new inputs.
Workaround: I used mouse and keyboard to re-select the unlock, but this would be an issue on controller only platforms.