- Debug Info:
In WP > WCOM > Debug info >
Make sure all sections are green. If there are RED or ORANGE sections, adjust your PHP and server settings.
- No Cache:
Since all data is fetched from WHMCS in real time, caching will not work, this includes WP-Cache and CloudFlare (or any other services like that)
- WHMCS URL:
Double check if WP > WCOM > WHMCS Config > WHMCS URL is exactly the same as in WHMCS > Settings > General Settings > WHMCS System URL
- SSL Certificate:
If you are using SSL for WHMCS, Check your WHMCS URL here for SSL problems. https://www.sslshopper.com/ssl-checker.html
- cURL optimization:
You can check these options to meet particular needs.
- use GET method for helper cURL requests
- send USERAGENT with cURL requests
- Authentication Failure for Invoices:
The authentication key is not validated during setup but is used for viewing invoices and some other functions, make sure it is setup correctly.
- If nothing helps, you can always open a ticket here http://support.whmpress.com
Other points that may be considered in some cases.
- If you are using .htaccess to limit access to WHMCS admin area, you should allow IP of the server where WP is hosted.
- Using GET to communication with WHMPress API can help in some situations. WCOM > advanced settings > Misclinious > use GET method for helper cURL requests > check.