Backup is not working

[llxx-lord-xxll]

PHP : 7.2.2
Laravel: 5.5.40
Laravel Admin: 1.5.x-dev

Description
I imported this extension just now.

But after clicking backup button, i face this issue

[lishuai199502]

I have the same trouble，internal error

[SamHz]

laravel:5.8
php:7.3.4
the same as them
No backups present