As the following screenshot, the URLs that were generated by custom GPTs have been lost, regardless of their creator. I am looking forward to an answer!
I have this same issue as well. Going on four weeks without any resolution. Crickets from OpenAI Support. This seems to be account related since it seems not to effect everyone.
I thought once the GPT Store went live there would be a deluge of people claiming links are not clickable in GPTs, but again, crickets.
Very strange in many respects.