I had 2 parent sites,which is modern and classic sites.When I installed my app to 2 site,it's fine. But when I created subsite from parent sites,app not working in subsites.But subsite have template blog(template default of MS) in group work still fine.

New contributor
Duc Dang is a new contributor to this site. Take care in asking for clarification, commenting, and answering. Check out our Code of Conduct.