Error while uploading backup to Google Drive

Hi, I am using your plugin to create backups but so far it has been unsuccessful in uploading the backups to Google Drive. I am getting the following Error Report from WordPress:

Error Details
=============
An error of type E_ERROR was caused in line 61 of the file /home/bonusser/schoolvisor.org/wp-content/plugins/everest-backup-google-drive/vendor/guzzlehttp/guzzle/src/functions.php. Error message: Uncaught Error: Call to undefined method GuzzleHttp\Utils::chooseHandler() in /home/bonusser/schoolvisor.org/wp-content/plugins/everest-backup-google-drive/vendor/guzzlehttp/guzzle/src/functions.php:61
Stack trace:
#0 /home/bonusser/schoolvisor.org/wp-content/plugins/wilcity-mobile-app/vendor/guzzlehttp/guzzle/src/HandlerStack.php(42): GuzzleHttp\choose_handler()
#1 /home/bonusser/schoolvisor.org/wp-content/plugins/wilcity-mobile-app/vendor/kreait/firebase-php/src/Firebase/Factory.php(621): GuzzleHttp\HandlerStack::create(NULL)
#2 /home/bonusser/schoolvisor.org/wp-content/plugins/wilcity-mobile-app/vendor/kreait/firebase-php/src/Firebase/Factory.php(467): Kreait\Firebase\Factory->createApiClient()
#3 /home/bonusser/schoolvisor.org/wp-content/plugins/wilcity-mobile-app/app/Database/FirebaseDB.php(58): Kreait\Firebase\Factory->createDatabase()
#4 /home/bonusser/schoolvisor.org/wp-content/plugins/wilcity-mobile-app/app/Database/FirebaseDB.php(34): WILCITY_APP\Database\FirebaseDB::_connect()
#5 /home/bonusser/sch

Kindly guide how to solve this issue. Thank you!