Hi ,
are you using Standard or Modern Customization and which BIG-IP version are you on?
I could successfully change the Header Logo in Access ›› Profiles / Policies : Customization : Quick Start/Basic.
In my test I was using 15.1.3 and I tried with Standard as well as Modern Customization.
The naming convention in K42811815 did not make a difference in my tests, I uploaded files named logo_xyz.png but also test_xyz.png.
I assume you clicked on Apply Access Policy?
On the filesystem the files are available in /var/sam/www/webtop/public/images/customization/Common/
[root@bigip01:Active:Standalone] Common # cd /var/sam/www/webtop/public/images/customization/Common/
[root@bigip01:Active:Standalone] Common # ll
total 16
drwxr-xr-x. 2 tomcat webservices 4096 Oct 14 17:53 access_demo01_general_ui
drwxr-xr-x. 2 tomcat webservices 4096 Oct 14 18:07 access_demo02_general_ui
-r--r--r--. 1 tomcat webservices 3803 Oct 14 18:07 logo_my_example2.png
-r--r--r--. 1 tomcat webservices 2448 Oct 14 17:52 logo_my_example.png
Once you go into one of the subfolders (e.g. access_demo01_general_ui) you will see that they contain a symlink to the logo in this folder.
[root@bigip01:Active:Standalone] Common # cd access_demo01_general_ui/
[root@bigip01:Active:Standalone] access_demo01_general_ui # ls -hla
total 12K
drwxr-xr-x. 2 tomcat webservices 4.0K Oct 14 17:53 .
drwxr-xr-x. 4 tomcat webservices 4.0K Oct 14 18:14 ..
lrwxrwxrwx. 1 root root 74 Oct 14 17:53 logo_image_en.png -> /var/sam/www/webtop/public/images/customization/Common/logo_my_example.png
Hope this helps.
KR
Daniel