Success! 
If you're still running into trouble, try using the following file in place of your certsage.php file. You'll need to change the .txt to .php just like you normally do when installing CertSage. You won't lose any of your existing ACME account data or configuration.
certsage.txt (32.9 KB)
The only thing I changed from version 1.4.1 was increasing the timeout between validation check attempts from 1 second to 2 seconds. Specifically, I changed sleep(1); on line 582 of certsage.php to sleep(2); . If many CertSage users keep encountering this problem, I'll make an official release with the fix. For now, please try this out and get back to me. Thanks. 