Hmm I wonder if you would need to also add the version number - /1.0 ? If the code does not work above then try this code.
# REQUEST METHODS FILTERED
# This filter is for blocking junk bots and spam bots from making a HEAD request, but may also block some
# HEAD request from bots that you want to allow in certains cases. This is not a security filter and is just
# a nuisance filter. This filter will not block any important bots like the google bot. If you want to allow
# all bots to make a HEAD request then remove HEAD from the Request Method filter.
# The TRACE, DELETE, TRACK and DEBUG request methods should never be allowed against your website.
RewriteEngine On
RewriteCond %{REQUEST_METHOD} ^(HEAD|TRACE|DELETE|TRACK|DEBUG) [NC]
RewriteCond %{HTTP_USER_AGENT} !^(UptimeRobot.*|another-example-good-bot) [NC]
RewriteRule ^(.*)$ - [F,L]