Upgrade Error

[hmaddy]

my current whmcs version is 8.3 and now i would like to upgrade it to 8.13 or latest LTS Version. but when i try to upgrade whmcs admin panel its throwing some error like this

Error (Help Documentation)
Error: proceeding.
ents/crons/). Please verify your existing installation configuration before
m crons directory could not be located as configured (/home/public_html/cli
A configuration file and/or existing installation has been found, but custo
In ComposerInstaller.php line n/a:
Script WHMCS\Installer\Composer\Hooks\ComposerInstallerHook::postUpdateCmd handling the post-update-cmd event terminated with an exception
-------------------------------------
WHMCS Installation/Update Assistant
-------------------------------------
> WHMCS\Installer\Composer\Hooks\ComposerInstallerHook::postUpdateCmd
Writing lock file
File signature was validated
Certificate used for signature validation was loaded and validated
File hash was validated. Hash: 6555de4e06a3a717faf7c8030737436c8e4c6a592df04c293e8c07122e80a252
- Installing whmcs/whmcs (8.13.1):Downloading(100%)Validating /home/user1/public_html/clients/vendor/whmcs/whmcs/53f6bd5053104db7d371b82992bde136.zip
Package operations: 1 install, 0 updates, 0 removals
Updating dependencies
Loading composer repositories with package information

[bear]

Lots missing from that, but did you keep the existing config file? That's where a custom cron directory is defined. If it's there and defined, make sure the actual directory exists still and so on. 

[wtools]

As mentioned above, Do you have a settings as shown below in your config file?

$crons_dir = '/home/username/whmcs_crons/';

Please see the value of the crons_dir and make sure the folder exist.