VM - Administrator Module not working after upgrade to 3.0.16

[php]

hi everyone,
I'm running joomla 3.5.1 and upgrade to VirtueMart 3.0.16 this moring. However, I found the VM - Administrator Module is not working after upgrade. All the others admin menu are working, such as system, users, menus, content, extensions and help. I clear all the caches and try disable and enable the module, but still same problem. I can't click the virtuemart and there is no drop down menu. The only way I can access virtuemart is through components--virtuemart.

Another weird problem is the virtuemart category page can only display when there is an item inside, otherwise the page will display" xxx.com page isn't working. xxx.com is currently unable to handle this request.HTTP ERROR 500". After add a new item in the category, the page will display properly.
Anyone can help? Thanks

PHP

[jenkinhill]

It is possible that you have a failed install of VM. Using Joomla's extensions manager install again the main VM component followed by the aio component. You don't lose any data or configuration by doing that.

http://forum.virtuemart.net/index.php?topic=123808.0

[php]

Thanks for the help. VM - Administrator Module is working after reinstall. However the empty category still not working. The error message shows " xxx.com page isn't working. xxx.com is currently unable to handle this request.HTTP ERROR 500". The page can only shows when there are items inside. Any advice? Thanks

[jenkinhill]

Now turn on VMdebug - Configuration/Shop/Advanced Settings: Enable debugging messages  to see if that shows the cause

And check the server error log. All 500s are recorded with the reason.

[Studio 42]

Now turn on VMdebug - Configuration/Shop/Advanced Settings: Enable debugging messages  to see if that shows the cause

And check the server error log. All 500s are recorded with the reason.

500 are never logged in PHP errors or Joomla errors but you can check the header in your browser >debug>network (F12 on PC) > header, some message are visible here, if you cannot display it another way else in preview tab sometime.

[jenkinhill]

Example of fatal error shown on the server log of one of my dev sites:
[09-Jun-2016 14:32:50 Europe/London] PHP Warning:  require(/home/liz1/public_html/new2/modules/mod_j51slideshow/tmpl/default.php): failed to open stream: No such file or directory in /home/liz1/public_html/new2/modules/mod_j51slideshow/mod_j51slideshow.php on line 19
[09-Jun-2016 14:32:50 Europe/London] PHP Fatal error:  require(): Failed opening required '/home/liz1/public_html/new2/modules/mod_j51slideshow/tmpl/default.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/liz1/public_html/new2/modules/mod_j51slideshow/mod_j51slideshow.php on line 19

[Studio 42]

This is the case for PHP error.
Joomla errors(db errors for eg) are not logged in php errors.