We are sorry for the trouble. The product team is aware of the issue, and they are currently working on a fix. I would request you to please be patient & stay tuned for updates. In the meantime, please use the workaround suggested by @Monika Gause. I hope it helps!
We are glad to inform you that this issue has been fixed in the latest Illustrator update, v26.2.1, released yesterday. I would request you to turn on the "Save in background" setting after updatingIllustrator and let us know how it goes.