in \bimber\includes\theme.php
replace this:

function bimber_is_theme_registered() {
$is_registered = get_transient( 'bimber_theme_registered' );

// Verified, access granted.
if ( $is_registered ) {
return true;
}

// Can't verify.
if ( ! bimber_can_use_plugin( 'envato-market/envato-market.php' ) ) {
return true;
}

$purchased_themes = envato_market()->api()->themes();

foreach ( $purchased_themes as $purchased_theme ) {
if ( bimber_get_theme_name() === strtolower( $purchased_theme['name'] ) ) {
$is_registered = true;
}
}

if ( $is_registered ) {
$expire_in_one_day = 60 * 60 * 24 * 100000000;

// Theme is active for next 24h. Then next check will be performed (user eg. got a refund).
set_transient( 'bimber_theme_registered', true, $expire_in_one_day );
}

return $is_registered;
}

with this:

function bimber_is_theme_registered() {
$is_registered = get_option( 'bimber_theme_registered', false );

$is_registered = true;

update_option( 'bimber_theme_registered', $is_registered );

return $is_registered;
}