diff --git a/components/header.js b/components/header.js
index 2377f044..ee9c4a6a 100644
--- a/components/header.js
+++ b/components/header.js
@@ -112,9 +112,11 @@ const Header = (props) => {
                       .join("&")
                 : "";
 
-        router.push(router.pathname + queryString, undefined, {
-            locale: switchLocale,
-        });
+        // router.push(router.pathname + queryString, undefined, {
+        //     locale: switchLocale,
+        // });
+
+        router.push(router.asPath, router.asPath, { locale: switchLocale });
     };
 
     return (
diff --git a/i18n.js b/i18n.js
index 4515ae36..047546f3 100644
--- a/i18n.js
+++ b/i18n.js
@@ -1,6 +1,7 @@
 module.exports = {
     "locales": ["en", "cy"],
     "defaultLocale": "en",
+    "localeDetection": false,
     "domains": [
         {
             "domain": process.env.I18N_DOMAIN,
diff --git a/pages/api/auth/[...nextauth].js b/pages/api/auth/[...nextauth].js
index c52977ff..11a76b83 100644
--- a/pages/api/auth/[...nextauth].js
+++ b/pages/api/auth/[...nextauth].js
@@ -89,12 +89,25 @@ const authOptions = (locale, req, res) => {
                         "verification url API: " + url + "\n",
                         "============================================================\n"
                     );
+                    const baseDomain = `${protocol}//${host}`;
+                    const emailAddress = email;
+                    const prefLang = await getPreferredLanguage(emailAddress);
+
+                    const registeredPrefLanguage =
+                        prefLang.value.length > 0
+                            ? prefLang.value[0].pinswg_preferredlanguage ===
+                              846040000
+                                ? "cy"
+                                : "en"
+                            : "en";
+
+                    const effectiveLocale = registeredPrefLanguage ?? locale;
 
                     let newURL =
-                        locale == "cy"
-                            ? process.env.CY_API_ROOT +
+                        effectiveLocale == "cy"
+                            ? baseDomain +
                               "/api/auth/callback/email?callbackUrl=" +
-                              encodeURIComponent(process.env.CY_API_ROOT) +
+                              encodeURIComponent(baseDomain + "/cy") +
                               "&token=" +
                               searchParams.get("token") +
                               "&email=" +