Fatal error: Uncaught Error: Class 'MBBParser\Arr' not found

When I am on the Edit Settings Page screen and click to update, I get a fatal error:

Fatal error: Uncaught Error: Class 'MBBParser\Arr' not found in
wp-content/plugins/meta-box-aio/vendor/meta-box/meta-box-builder/modules/settings-page/src/Parser.php:28
Stack trace:
#0 /wp-content/plugins/meta-box-aio/vendor/meta-box/meta-box-builder/modules/settings-page/src/Parser.php(9): MBB\SettingsPage\Parser->parse_menu_icon()
#1 /wp-content/plugins/meta-box-aio/vendor/meta-box/meta-box-builder/modules/settings-page/src/Edit.php(41): MBB\SettingsPage\Parser->parse()
#2 /wp-content/plugins/meta-box-aio/vendor/meta-box/meta-box-builder/src/BaseEditPage.php(49): MBB\SettingsPage\Edit->save(3046, Object(WP_Post))
#3 /wp-includes/class-wp-hook.php(294): MBB\BaseEditPage->save_wrapper(3046, Object(WP_Post))
#4 /wp-includes/class-wp-hook.php(316): WP_ in /wp-content/plugins/meta-box-aio/vendor/meta-box/meta-box-builder/modules/settings-page/src/Parser.php on line 28

The changes are saved even with this error. Interestingly, on my local install, I see the icon type and icons, but on my published site I see the icon grid in a flash but it's not visible when the page loads. I get the same error on both environments.

Additionally, the link to the settings page does not show up in the left menu.

Finally, when I click the Generate in the "Get PHP code" panel, the message "Generating code, please wait..." appears but no code appears.

I've uninstalled and reinstalled. I've turned off all plugins and tried again. Any other suggestions for troubleshooting this?

Thank you!!