Issue with emails copied from one account to another not showing up on gmail.com

I recently created a new gmail account and I am using it as my primary. I have several gmail accounts that I want to close and I am moving my folders w/ emails from these older gmail accounts to my new one. I have my gmail accts linked to Mail on MacBook Air as well as my iPad and iPhone. All 3 are on the newest versions.

Yesterday, I copied all of the folders from the old gmail accounts to the new ones using Mail on the MacBook. I confirmed the folders and emails were showing up on the new account in the MacBook Mail. I then deleted the folders in the old gmail accounts.

In Macbook Mail, I see all of the folders with all of the emails on the new gmail account. When I go to gmail.com, iPhone and iPad, I can see the folders but there are no emails inside of them. It seems that whatever I did did not sync up with the gmail server. I have tried moving one back to its original gmail account to see if that works, but the same thing happens. It is fine on MacBook, but elsewhere I can see the folder but not the emails.

Any suggestions on how to get this fixed so I can get the emails into gmail & my other devices. I have many years of emails on there that I do not want to lose.

Thank you!