If you find you cannot (or no longer) connect to your GKE cluster, and see a message like
executable gke-gcloud-auth-plugin not found
make sure that you installed the gcloud tools from the same kind of shell that Lens uses for its terminal shell. If, for instance, you installed the gcloud tools from bash then the gcloud setup may have modified your .bash_profile to make sure the PATH environment variable includes the path to the gcloud tools. From Lens go to the Terminal preferences (Lens → Preferences → Terminal on Mac, File → Preferences → Terminal on Windows and Linux) and make sure the TERMINAL SHELL PATH is set to the same shell that you installed the gcloud tools from.
Alternatively, if you want Lens to use a different kind of shell then edit the appropriate shell initialization file (e.g. .zprofile for zsh) to similarly set the gcloud tools path in the PATH.
Also, it may be that you need to refresh the kubeconfig, especially if you’ve made changes to your gcloud installation.
As per https://cloud.google.com/kubernetes-engine/docs/how-to/cluster-access-for-kubectl you can get credentials, which updates your kubeconfig, by running:
gcloud container clusters get-credentials CLUSTER_NAME --region=COMPUTE_REGION
If that doesn’t help, first make sure you can still connect to the cluster from a terminal using kubectl. Then try launching Lens from the same terminal, e.g. on a mac:
/Applications/Lens.app/Contents/MacOS/Lens
(Make sure Lens isn’t already running by first quitting it from the tray, or from the Lens or File menu)
If you installed gcloud in WSL and are running the Windows version of Lens check this out.
If this doesn’t help post your detailed issue here on the forum.