Q:

Can't log in to Admin CP after updating from 2.6.1 to 2.7.3

I've just finished updating my EE installation from 2.6.1 to 2.7.3 but now that the update is complete I cannot log in. I can access the login page but when I enter my credentials it tries to load http://mysite.com/admin.php?S=0&D=cp&C=login&M=authenticate but it just hangs there forever.
Some things I have tried based on similar issues I found on the EE forum:

Tried using a different browser
Tried clearing browser cache and deleting EE cache folder
Tried adding $config[‘admin_session_type’] = “c” to config.php
Tried adding $assign_to_config[‘cookie_prefix’] = “site_name” to index.php and admin.php
Tried enabling debug mode in index.php and admin.php(did not get any errors when trying to load the Admin CP but when I try to load the homepage I am getting the following error:
Fatal error: Class PT_Fieldtype contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (EE_Fieldtype::display_field) in \system_EE\expressionengine\third_party\pt_field_pack\pt_fieldtype.php on line 148

Any ideas? Thanks in advance!

A:

The error message is pointing to an issue with Pixel and Tonic's Field Pack; you should attempt to upgrade it.
These "white screens of death" errors with the control panel after updating are frequently caused by an issue with an add-on; you temporarily disable them by adding  $config['allow_extensions'] = "n"; to your config.php. 

