Errors on activation

I get the following errors when I activate the plugin:

Deprecated: Non-static method WPVC_Map_Widget::load_widget() should not be called statically in C:\htdocs\site\apps\cms\wp-includes\class-wp-hook.php on line 286

Deprecated: Non-static method WPVC_Master::init() should not be called statically in C:\htdocs\site\apps\cms\wp-includes\class-wp-hook.php on line 286

Deprecated: Non-static method WPVC_Master::add_pages() should not be called statically in C:\htdocs\site\apps\cms\wp-includes\class-wp-hook.php on line 286

Notice: Undefined index: hex_smap_button in C:\htdocs\site\apps\cms\wp-content\plugins\wp-visited-countries-reloaded\inc\class-wpvc-settings.php on line 536

Notice: Undefined index: pos_smap_button in C:\htdocs\site\apps\cms\wp-content\plugins\wp-visited-countries-reloaded\inc\class-wpvc-settings.php on line 537

Deprecated: Non-static method WPVC_Master::check_version() should not be called statically in C:\htdocs\site\apps\cms\wp-includes\class-wp-hook.php on line 288

Deprecated: Non-static method WPVC_Master::check_version() should not be called statically in C:\htdocs\site\apps\cms\wp-includes\class-wp-hook.php on line 288

Deprecated: Non-static method WPVC_Master::admin_notice() should not be called statically in C:\htdocs\site\apps\cms\wp-includes\class-wp-hook.php on line 286
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The plugin generated 595 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.

I’m using WP 4.9.10 with PHP 7.2.

I see someone else posted the same issue and it was closed and marked as resolved, but there was no solution posted.

Any help would be greatly appreciated.