diff --git a/native/account/registration/existing-ethereum-account.react.js b/native/account/registration/existing-ethereum-account.react.js
--- a/native/account/registration/existing-ethereum-account.react.js
+++ b/native/account/registration/existing-ethereum-account.react.js
@@ -1,7 +1,10 @@
 // @flow
 
 import * as React from 'react';
-import { Text } from 'react-native';
+import { Text, Alert } from 'react-native';
+
+import { siweAuthActionTypes } from 'lib/actions/siwe-actions.js';
+import { createLoadingStatusSelector } from 'lib/selectors/loading-selectors.js';
 
 import RegistrationButtonContainer from './registration-button-container.react.js';
 import RegistrationButton from './registration-button.react.js';
@@ -9,7 +12,12 @@
 import RegistrationContentContainer from './registration-content-container.react.js';
 import type { RegistrationNavigationProp } from './registration-navigator.react.js';
 import type { NavigationRoute } from '../../navigation/route-names.js';
+import { useSelector } from '../../redux/redux-utils.js';
 import { useStyles } from '../../themes/colors.js';
+import { useSIWEServerCall } from '../siwe-hooks.js';
+
+const siweAuthLoadingStatusSelector =
+  createLoadingStatusSelector(siweAuthActionTypes);
 
 export type ExistingEthereumAccountParams = {
   +message: string,
@@ -21,12 +29,27 @@
   +route: NavigationRoute<'ExistingEthereumAccount'>,
 };
 function ExistingEthereumAccount(props: Props): React.Node {
-  const styles = useStyles(unboundStyles);
+  const siweServerCallParams = React.useMemo(() => {
+    const onServerCallFailure = () => {
+      Alert.alert('Unknown error', 'Uhh... try again?', [{ text: 'OK' }], {
+        cancelable: false,
+      });
+    };
+    return { onFailure: onServerCallFailure };
+  }, []);
+  const siweServerCall = useSIWEServerCall(siweServerCallParams);
 
-  const { goBack } = props.navigation;
+  const { params } = props.route;
+  const onProceedToLogIn = React.useCallback(() => {
+    siweServerCall(params);
+  }, [siweServerCall, params]);
 
-  const onProceedToLogIn = React.useCallback(() => {}, []);
+  const siweAuthCallLoading = useSelector(
+    state => siweAuthLoadingStatusSelector(state) === 'loading',
+  );
 
+  const { goBack } = props.navigation;
+  const styles = useStyles(unboundStyles);
   return (
     <RegistrationContainer>
       <RegistrationContentContainer>
@@ -42,7 +65,7 @@
         <RegistrationButton
           onPress={onProceedToLogIn}
           label="Log in to account"
-          variant="enabled"
+          variant={siweAuthCallLoading ? 'loading' : 'enabled'}
         />
         <RegistrationButton
           onPress={goBack}