There are 2 settings you have to be sure you've set correctly in order to view other users' estimates.
Setting 1: Security Permission to View Others' Estimates
Your user account must have permission to estimating set to COMPANY ADMINISTRATOR. DEFAULT permission only allows estimators to view/edit their own estimates.
Note: Only the security admin on your company account can change/edit your security permissions.
Setting 2: Estimate Screen Set to Show Me: All Company Estimates
On the list of estimates, you can choose whether you want to view just My Estimates or All Company Estimates. You will only see this option if you have the estimating security permission set to Company Administrator (step 1).