Troubleshooting a 404 Page Not Found Error in the Admin Area
When navigating to various sections (In this example, the Setup >> Notifications section) of the Admin Area, you are presented with an error similar to this:
As you can see in the URL, we are generating a more SEO Friendly link instead of a link using variables (ie index.php?rp=/admin/setup). Unfortunately this is not rendering the page properly.
The error message 404 Page Not Found occurring in the Admin Area may be caused by an outdated htaccess file.
There are a few options we have to resolve this issue. We will review them all below and you can choose which is the best course of action for your situation.
Updating the htaccess file
Updating the htaccess file is the preferred method of resolution. htaccess is only supported in Apache-based web servers. If you are using nginx this method will not work. Please do note that WHMCS does not test on any webservers except for Apache.
First, head back to your main Admin Area URL. From there, navigate to Setup >> General Settings
Within the General Settings, scroll to the bottom of the page to the Friendly URLs section. From here, you may note that this setting is being manually overridden. By default, WHMCS will detect and pick the best option for your server environment.
As you can see in the screenshot, ours has been manually overridden and is good indicator that something may not be setup properly. From this, choose Advanced Settings on the right-hand side of this section.
A new modal will popup with some important information. As you can see, we are manually overriding the settings that are available. In our case, Full Friendly Rewrite did not pass the WHMCS test and is marked as such. No worries! Our next step is to try and correct this. Choose the Rewrite tab to continue.
On the next screen you can see that our htaccess rules are out of date. We recommend enabling the Auto-Managed Rewrite setting. Go ahead and do that, then press Synchronize then Close the modal
Once closed, click on the Refresh icon for the Friendly URLs section to see what WHMCS can now detect. As you can see, the newly detected setting is Full Friendly Rewrite and the sections previously showing a 404 error now work!
Reverting the Friendly URL Mode to Basic
WHMCS tried to automatically detect the proper Friendly URL mode. Sometimes SysAdmins do lock down servers too much and that makes WHMCS unable to detect the Friendly Modes available. In this case, the easiest way to get your system back up and running is to switch to the Basic URLs for Friendly URLs. This will ensure the links are set to the traditional URL that does not require mod_rewrite or any other server-side rules to render.
To get started, navigate to Setup >> General Settings
Scroll to the bottom of the page to the Friendly URLs section. From the dropdown, choose Basic URLs and press Save Changes.
Upon doing this, all of the previously Friendly-styled URLs will be reverted to a basic format and should render your system usable again!