In logs/errors I was seing this:
PHP Parse error: syntax error, unexpected T_PAAMAYIM_NEKUDOTAYIM, expecting ')' in .../plugins/google_ads/google_ads.php on line 67
I changed the line 67 from
'plugin' => $plugin::about($keys),
into
'plugin' => $plugin->about($keys),
and the error went away, but I am still not able to see the ads