Why does Android Studio build fail after main class rename?

I renamed the base class of my app before uploading to the Play Store and successfully completed a build and uploaded to the Play store.

com.app.bgd2.Bgd2Activity became com.app.bgd.Bgd2Activity

Now the second time I try to build, even after doing build clean from the android studio menus, and gradle clean on the command line I see this error:

Activity class {com.app.bgd2/com.app.bgd.Bgd2Activity} does not exist

So doing a grep for any file with the old string com.app.bg2 fails to find any appearance of the old string.

find . -type f  -exec grep bgd2 {} \;

What would cause this error? Is there another cache or other file to check that is outside the project folder/files?

What it looks like in the actual project:

--- a/android/app/src/main/java/com/scripturial/bgd2/Bgd2Activity.java
+++ b/android/app/src/main/java/com/scripturial/bgd/Bgd2Activity.java
@@ -1,8 +1,8 @@

-package com.scripturial.bgd2;
+package com.scripturial.bgd;

--- a/android/app/build.gradle
+++ b/android/app/build.gradle
@@ -5,13 +5,13 @@ plugins {
def buildWithCMake = project.hasProperty('BUILD_WITH_CMAKE');

android {
-    namespace = "com.scripturial.bgd2"
+    namespace = "com.scripturial.bgd"

And an actual screenshot,

I have discovered an older version of this same question, but the solutions proposed do not work with the latest version of Android Studio. Older version

After trying all of the solutions listed [here](Package rename and error "Activity class does not exist") none of them worked. I upgraded gradle from 8.7 to 8.10 using the plugin menu, and that made the problem go away.

I am unsure of what the underlying cause of this error was, but at least it fixed the problem. So I am recording it here as the answer to this problem in case anyone else has this problem.