Catch invalid param error too

src/AddThreepid.ts

@@ -149,6 +149,8 @@ export default class AddThreepid {
                 throw new UserFriendlyError("settings|general|msisdn_in_use", { cause: err });
             } else if (err instanceof MatrixError && err.errcode === "M_THREEPID_MEDIUM_NOT_SUPPORTED") {
                 throw new UserFriendlyError("settings|general|msisdn_adding_unsupported_by_hs", { cause: err });
+            } else if (err instanceof MatrixError && err.errcode === "M_INVALID_PARAM") {
+                throw new UserFriendlyError("settings|general|invalid_phone_number", { cause: err });
             }
             // Otherwise, just blurt out the same error
             throw err;

src/i18n/strings/en_EN.json

@@ -2533,6 +2533,7 @@
             "error_share_msisdn_discovery": "Unable to share phone number",
             "identity_server_no_token": "No identity access token found",
             "identity_server_not_set": "Identity server not set",
+            "invalid_phone_number": "The phone number supplied does not appear to be valid.",
             "language_section": "Language",
             "msisdn_adding_unsupported_by_hs": "This homeserver does not support adding phone numbers to your account.",
             "msisdn_in_use": "This phone number is already in use",