Support intro
Sorry to hear you’re facing problems 
help.nextcloud.com is for home/non-enterprise users. If you’re running a business, paid support can be accessed via portal.nextcloud.com where we can ensure your business keeps running smoothly.
In order to help you as quickly as possible, before clicking Create Topic please provide as much of the below as you can. Feel free to use a pastebin service for logs, otherwise either indent short log examples with four spaces:
example
Or for longer, use three backticks above and below the code snippet:
longer
example
here
Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can 
Nextcloud version (eg, 12.0.2): 14.0.2
Operating system and version (eg, Ubuntu 17.04): Linux Mint 18.3 (Kernel 4.18.12-041812-generic)
Apache or nginx version (eg, Apache 2.4.25): nginx version: nginx/1.10.3 (Ubuntu)
PHP version (eg, 7.1): PHP 7.0.32-0ubuntu0.16.04.1 (cli) ( NTS )
The issue you are facing:
Newly uploaded photos do not have a preview generated.
Error Message is "Error! Could not generate a preview of this file
Is this the first time you’ve seen this error? (Y/N): Y
Steps to replicate it:
- Upload a jpg file using WebUI or Android client
- Click on file in Nextcloud (no thumbnail present)
- Blank screen with error message displayed
The output of your Nextcloud log in Admin > Logging:
|Error|gallery|Exception: Preview generation has failed|2018-10-11T16:02:43+0100|
| --- | --- | --- | --- |
|Error|gallery|OCP\Files\NotFoundException:|2018-10-11T16:02:43+0100|
|Debug|no app in context|No cache entry found for /appdata_ocjakydyp1vm/preview/1003276 (storage: local::/home/jonathan/WD2TB/nextcloud/data/, internalPath: appdata_ocjakydyp1vm/preview/1003276)|2018-10-11T16:02:43+0100|
|Debug|core|OC_Image->fixOrientation() Orientation: -1|
The output of your config.php file in `/path/to/nextcloud` (make sure you remove any identifiable information!):
The output of your Apache/nginx/system log in /var/log/____:
86.8.128.238 - - [11/Oct/2018:16:08:52 +0100] "GET /nextcloud/index.php/apps/gallery/slideshow HTTP/2.0" 200 1058 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36"
86.8.128.238 - - [11/Oct/2018:16:08:52 +0100] "GET /nextcloud/index.php/core/preview?fileId=1003271&c=4b3f5ca23d2f05dee2db1bfb9d0fa586&x=32&y=32&forceIcon=0 HTTP/2.0" 404 606 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36"
86.8.128.238 - - [11/Oct/2018:16:08:52 +0100] "GET /nextcloud/index.php/core/preview?fileId=1003267&c=158a9850f6c5538f591eebd4c2a59e5f&x=32&y=32&forceIcon=0 HTTP/2.0" 404 604 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36"
86.8.128.238 - - [11/Oct/2018:16:08:52 +0100] "GET /nextcloud/index.php/apps/gallery/preview/1003276?width=1700&height=1700&c=34319c993b1b82e09131a5562ed73dbc&requesttoken=V4NhYvoyjZRt%2FxnHuXgsOVAJYBppYJKitvYoFMcqmJY%3D%3AJrYgO4xF1OIGiGmokitVdzdrVSwCUuPp8c9bcaRj%2FKE%3D HTTP/2.0" 500 705 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36"