diff --git a/README.md b/README.md
index 1f7b04a..8caa74b 100644
--- a/README.md
+++ b/README.md
@@ -9,9 +9,14 @@ The latest version is Version 1.3. To install or update Math Symbols Input:
 
 1. Download the [installer for the latest version](https://github.com/knrafto/MathSymbolsInput/releases/latest/download/MathSymbolsInput.pkg).
 2. Open the installer and continue through the installation steps.
-3. Log out and log back in (or reboot).
-
-The installer can enable the input method automatically. If you want to configure input sources, see the [macOS help page on input sources](
+3. **macOS 15 (Sequoia) and later**: Due to security restrictions, you will need to manually enable the input method after installation:
+   - Go to **System Settings → Keyboard → Input Sources**
+   - Click the **+** button
+   - Find **Math Symbols Input** under English
+   - Add it to your input sources
+4. Log out and log back in (or reboot).
+
+On macOS 14 (Sonoma) and earlier, the installer can enable the input method automatically. For more information about configuring input sources, see the [macOS help page on input sources](
 https://support.apple.com/guide/mac-help/type-language-mac-input-sources-mchlp1406/mac).
 
 # Usage
@@ -38,6 +43,17 @@ New commands will take effect immediately.
 
 # FAQ
 
+## The input method isn't working after installation on macOS 15 or later
+
+Starting with macOS 15 (Sequoia), Apple introduced security restrictions that prevent third-party input methods from being enabled automatically during installation. You need to manually enable Math Symbols Input:
+
+1. Go to **System Settings → Keyboard → Input Sources**
+2. Click the **+** button
+3. Find **Math Symbols Input** under English
+4. Add it to your input sources
+
+After adding the input method, you can switch to it using the input source menu in the menu bar or with the keyboard shortcut (typically Control+Space or Control+Option+Space).
+
 ## Are there Windows or Linux versions?
 
 Not yet, but hopefully soon.
diff --git a/activate/main.m b/activate/main.m
index 6fa84f5..08e000c 100644
--- a/activate/main.m
+++ b/activate/main.m
@@ -1,13 +1,36 @@
 #import <Carbon/Carbon.h>
+#import <Cocoa/Cocoa.h>
 
 static const char *kInstallLocation = "/Library/Input Methods/Math Symbols Input.app";
 static NSString *kProcessName = @"Math Symbols Input";
 static NSString *kSourceID = @"com.mathsymbolsinput.inputmethod.MathSymbolsInput";
 
-static void logIfError(OSStatus status, NSString *message) {
+static BOOL logIfError(OSStatus status, NSString *message) {
   if (status != noErr) {
     NSError *error = [NSError errorWithDomain:NSOSStatusErrorDomain code:status userInfo:nil];
     NSLog(@"%@: %@", message, [error localizedDescription]);
+    return YES;
+  }
+  return NO;
+}
+
+static BOOL isMacOS15OrLater(void) {
+  NSOperatingSystemVersion version = [[NSProcessInfo processInfo] operatingSystemVersion];
+  return version.majorVersion >= 15;
+}
+
+static void showManualActivationDialog(void) {
+  NSAlert *alert = [[NSAlert alloc] init];
+  [alert setMessageText:@"Math Symbols Input Installation Complete"];
+  [alert setInformativeText:@"Due to macOS security restrictions, you need to manually enable the input method:\n\n1. Go to System Settings → Keyboard → Input Sources\n2. Click the + button\n3. Find \"Math Symbols Input\" under English\n4. Add it to your input sources\n\nWould you like to open System Settings now?"];
+  [alert setAlertStyle:NSAlertStyleInformational];
+  [alert addButtonWithTitle:@"Open System Settings"];
+  [alert addButtonWithTitle:@"Later"];
+
+  NSModalResponse response = [alert runModal];
+
+  if (response == NSAlertFirstButtonReturn) {
+    [[NSWorkspace sharedWorkspace] openURL:[NSURL URLWithString:@"x-apple.systempreferences:com.apple.Keyboard-Settings.extension"]];
   }
 }
 
@@ -63,9 +86,26 @@ int main(int argc, const char *argv[]) {
     [NSThread sleepForTimeInterval:1.0];
 
     NSLog(@"Enabling input source %@", kSourceID);
-    logIfError(TISEnableInputSource(inputMethod), @"Could not enable input source");
+    OSStatus enableStatus = TISEnableInputSource(inputMethod);
+    BOOL enableFailed = logIfError(enableStatus, @"Could not enable input source");
     [NSThread sleepForTimeInterval:1.0];
 
+    // Check if the input method is actually enabled after attempting to enable it
+    BOOL isEnabled = CFBooleanGetValue(TISGetInputSourceProperty(inputMethod, kTISPropertyInputSourceIsEnabled));
+
+    if (!isEnabled || enableFailed) {
+      NSLog(@"Input source could not be automatically enabled. Manual activation required.");
+
+      // On macOS 15 (Sequoia) and later, automatic activation is blocked by security restrictions
+      if (isMacOS15OrLater()) {
+        NSLog(@"Detected macOS 15 or later. Showing manual activation instructions.");
+        showManualActivationDialog();
+      }
+
+      CFRelease(inputSources);
+      return 0;
+    }
+
     NSLog(@"Selecting input source %@", kSourceID);
     logIfError(TISSelectInputSource(inputMethod), @"Could not select input source");