2.5 Upgrade to 3.5 some pages no work on back-end - Joomla! Forum - community, help and support

hi
tried upgrade 2.5 3.5 on sub-directory(copy root joomla-website , database).

ex:
https://www.cloudgood.org -> (joomla 2.5)
https://www.cloudgood.org/a3test ->(joomla 2.5 3.5 test)

it upgraded 2 pages can work on backend(control panel , extension manager).
other pages display nothing.

work page:


not work page:



when upgrading via "joomla! update" , error message

"1091 can't drop 'usertype' xxxxx " ...

so excute sql scripts avoid error before upgrading.

alter table jos_users add index (usertype);
alter table jos_session add column whosonline int;
alter table jos_session add index (whosonline);
alter table jos_redirect_links add column idx_link_old int;
alter table jos_redirect_links add index (idx_link_old);

i need issue . don't have idea solve it.
help !!!!!

hi
1. set $error_reporting='maximum' in configuration.php file , post errors.
2. please run viewtopic.php?f=621&t=582860 , post results.