Server error 500 after upgrade and possible solution

After upgrading the database from 1.5.4 to 1.5.5e I got the famous Server error 500 when opening the admin section. I spend some time googling for the answer. After some trial and error it turned out to be the missing language files. After adding the language pack all worked fine again. Maybe this solution can be added to the list of possible causes for error 500.

This is an issue that will be happening on every database upgrade when the infromation in the database differs from the actual site.

Maybe that this item cab be of help to someone .

What specific errors were you seeing recorded in the /logs/ directory on your server?
Those will be more helpful data for people trying to diagnose the problem if they run into it themselves.

In Apache logs I found also references to the templates. An abstract:
[Sun Aug 20 19:36:42.274155 2017] [authz_core:error] [pid 3312:tid 1896] [client ::1:64880] AH01630: client denied by server configuration: E:/xampp7/htdocs/zc155/includes/templates/template_default/images/HEADER_LOGO_IMAGE, referer: http://localhost/zc155/
[Sun Aug 20 19:36:45.922772 2017] [authz_core:error] [pid 3312:tid 1880] [client ::1:64879] AH01630: client denied by server configuration: E:/xampp7/htdocs/zc155/includes/templates/template_default/images/HEADER_LOGO_IMAGE, referer: http://localhost/zc155/index.php?mai...index&cPath=66
[Sun Aug 20 19:36:46.071870 2017] [authz_core:error] [pid 3312:tid 1904] [client ::1:64882] AH01630: client denied by server configuration: E:/xampp7/htdocs/zc155/includes/templates/template_default/buttons/dutch, referer: http://localhost/zc155/index.php?mai...index&cPath=66
[Sun Aug 20 19:36:46.120903 2017] [authz_core:error] [pid 3312:tid 1896] [client ::1:64880] AH01630: client denied by server configuration: E:/xampp7/htdocs/zc155/includes/templates/template_default/buttons/dutch, referer: http://localhost/zc155/index.php?mai...index&cPath=66
[Sun Aug 20 19:36:46.140916 2017] [authz_core:error] [pid 3312:tid 1864] [client ::1:64884] AH01630: client denied by server configuration: E:/xampp7/htdocs/zc155/includes/languages/dutch, referer: http://localhost/zc155/index.php?mai...index&cPath=66
[Sun Aug 20 19:36:46.141918 2017] [authz_core:error] [pid 3312:tid 1880] [client ::1:64879] AH01630: client denied by server configuration: E:/xampp7/htdocs/zc155/includes/templates/template_default/buttons/dutch, referer: http://localhost/zc155/index.php?mai...index&cPath=66
[Sun Aug 20 19:36:46.179945 2017] [authz_core:error] [pid 3312:tid 1896] [client ::1:64880] AH01630: client denied by server configuration: E:/xampp7/htdocs/zc155/includes/templates/template_default/buttons/dutch, referer: http://localhost/zc155/index.php?mai...index&cPath=66

Ok, but what about the folder called logs that is in the catalog and adjacent to folders such as images, includes, downloads, pub, etc? Not everyone has access to the apache logs, but ought to be able to access their (Zen Cart) logs directory. Files there will have start with myDebug-...


/admin
/cache
/docs
/downloads
/extras
/images
/includes
/logs <-- this folder
/media
/pub
ajax.php
index.php
ipn_handler.php
nddbc.html