You can always use a back up file. Though it is rare is not showing you a battle you must complete, are you sure you're at the Secret Shrine.? Also for further reference, post Rejuvenation content on Rejuvenation sub-forums.
If you already have the egg in hands, you can go and check in your Pokemon Reborn battlers folder. Or you can take a screenshot and maybe I can tell you.
You must also buy all pokemon at 7th Street. This guide should help you in order to fulfill it.
https://pokemon-reborn.fandom.com/wiki/Mega-Z_Ring_Sidequest
Seems that mostly people are in Scorbunny/Grookey Squad.. I really love fire starters, but I got a bad feeling that it will turn out to be Fire/Fighting again, plus, it seems to cute to be a fire type imo, lol. Tbh, I don't like Grookey. I would pick for sure Sobble, at first glance it seems I'm watching a newer Froakie imo. I hope its final form to be useful, from the three I like its design most. And got the feeling that its final form will make you sob.
Charizard, Garchomp, Rhyperior, Hydreigon, Kyogre, Rayquaza, Sceptile, Salamance, Flareon, Haxorus and Torterra. Would you mind selecting a pokemon from above?
You can't deal with it. There are only two things for sure in life, Taxes and Death. That's why we must live to the fullest and with no regrets. Sounds cruel.
I'll hope you overcome whatever problem you have.