The problem that I had was I installed Gitea and selected the second admin account to be the admin. Yunohost created the first admin account as an account, but not an administrator.
By following these directions, I was able to create a new administrator account.
I came across this post on this forum: Add user to single app (gitea) but not ynh - Support apps - YunoHost Forum
The useful part of the post was this:
cd /opt/gitea
sudo -u gitea gitea admin user create --name ...
I also came across this other post: gitea: create admin user - ricardo malla’s blog
Which contained this:
gitea admin user create --admin --username [username]--password [password] --email [emailaddress]
I was able to create an admin account using this command:
cd /opt/gitea
sudo -u gitea gitea admin user create --admin --username myuser --password mypassword --email myemail
I hope that this post will be useful to anyone else who has the same problem.