1. Patch argocd secret to update password

kubectl -n argocd patch secret argocd-secret  -p '{"data": {"admin.password": null, "admin.passwordMtime": null}}'

     2. Restart the api-server pod by deleting pod directly or by scaling the pod replica to zero and then back to one

kubectl -n argocd scale deployment argocd-server --replicas=0
# once scaled-down, make sure to scale back up and wait a few minutes before
kubectl -n argocd scale deployment argocd-server --replicas=1

Now get the password by following command

kubectl -n argocd get secret argocd-initial-admin-secret -o jsonpath="{.data.password}" | base64 -d

Now you can login and reset the password from argocd dashboard.