Unable to Edit Case Record > This case cannot be edited because it was closed XX or more days ago (Edit button not available).

Based on the Help article Locked Cases, users other than the Administrator cannot edit the case when Lock Closed Cases After Lockout Period box is checked. To resolve this, perform the following steps:

1.    Navigate to Setup > Support > Support Preferences.

2.    In General tab > Case Lockout section, deselect Lock Closed Cases After Lockout Period.

3.    Click Save.