diff --git a/aio/content/errors/NG6999.md b/aio/content/errors/NG6999.md
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+@name Invalid metadata
+@category compiler
+@shortDescription Invalid @NgModule() metadata
+
+@description
+This error represents the import or export of an `@NgModule()` that doesn't have valid metadata.
+
+@debugging
+The library might have been processed with `ngcc`.
+If this is the case, try removing and reinstalling `node_modules`.
+This error is likely due to the library being published for Angular Ivy, which cannot be used in this View Engine application.
+If that is not the case then it might be a View Engine based library that was converted to Ivy by ngcc during a postinstall step.
+
+Check the peer dependencies to ensure that you're using a compatible version of Angular.