Fatal Error Breaking whole website

Iitially set standard working hours, Mon – Fri for company. Things have changed. The employee is only working specific days – so deleted Mon – Fri general settings and employee standard dates, added in Special Dates, now website completely broken

Fatal error: Uncaught AmeliaBooking\Domain\Common\Exceptions\InvalidArgumentException: Invalid key 1. in /home/proaesthetics/public_html/wp-content/plugins/ameliabooking/src/Domain/Collection/AbstractCollection.php:88 Stack trace: #0 /home/proaesthetics/public_html/wp-content/plugins/ameliabooking/src/Application/Services/User/ProviderApplicationService.php(1335): AmeliaBooking\Domain\Collection\AbstractCollection->getItem(1) #1 /home/proaesthetics/public_html/wp-content/plugins/ameliabooking/src/Application/Services/Stash/StashApplicationService.php(393): AmeliaBooking\Application\Services\User\ProviderApplicationService->getProviderServiceLocations(Object(AmeliaBooking\Domain\Entity\User\Provider), Object(AmeliaBooking\Domain\Collection\Collection), Object(AmeliaBooking\Domain\Collection\Collection)) #2 /home/proaesthetics/public_html/wp-content/plugins/ameliabooking/src/Infrastructure/WP/ShortcodeService/AmeliaShortcodeService.php(164): AmeliaBooking\Application\Services\Stash\StashApplicationService->getStash() #3 /ho in?/home/proaesthetics/public_html/wp-content/plugins/ameliabooking/src/Domain/Collection/AbstractCollection.php?on line?88

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