Have you got Google home on your mobile? I had to download Google calendar on my phone for it to work.
Have you tried pressing the Mike on magic remote? This brings up options first try.
Are the tv/google home on phone, both on the same Wi-Fi channel?
I found, with the Google assistant, any previous entries in your calendar will not be recognised. I had to re input diary dates verbally to Google for new diary entries, it then recognised them and worked ok.