Clarified error message for non-writable options table. (#17767)

When the wp_options table is not writeable, connecting Jetpack will result in the error Verification secrets not found.
This PR clarifies the error, informing the user that they need to confirm the options table is writable.

packages/connection/src/class-manager.php

@@ -829,6 +829,10 @@ public function register( $api_endpoint = 'register' ) {
 		add_action( 'pre_update_jetpack_option_register', array( '\\Jetpack_Options', 'delete_option' ) );
 		$secrets = $this->generate_secrets( 'register', get_current_user_id(), 600 );
 
+		if ( false === $secrets ) {
+			return new WP_Error( 'cannot_save_secrets', __( 'Jetpack experienced an issue trying to save options (cannot_save_secrets). We suggest that you contact your hosting provider, and ask them for help checking that the options table is writable on your site.', 'jetpack' ) );
+		}
+
 		if (
 			empty( $secrets['secret_1'] ) ||
 			empty( $secrets['secret_2'] ) ||
@@ -1330,8 +1334,8 @@ public function generate_secrets( $action, $user_id = false, $exp = 600 ) {
 
 		$secrets[ $secret_name ] = $secret_value;
 
-		\Jetpack_Options::update_raw_option( self::SECRETS_OPTION_NAME, $secrets );
-		return $secrets[ $secret_name ];
+		$res = Jetpack_Options::update_raw_option( self::SECRETS_OPTION_NAME, $secrets );
+		return $res ? $secrets[ $secret_name ] : false;
 	}
 
 	/**