on accessing subsites access is denied even given access.

i have created sub sites like site1 -> subsite1-1 - > subsite 1-1-1

now problem is that when i give readonly access to on just subsite1-
1-1 user added successfully but when user try to access website site
is not accessible.

user not able to access site, access request page open after some
attempts each site has unique permission.

on accessing subsites access is denied even given access.

kindly tell whats the problem and how to fix it.