Why does the regular expression in logrt.count not work in Zabbix?

Question

Zabbix

Good day!

I create an item with a key:

logrt.count["/var/www/app/log/action.log","SOME_STRING","UTF-8"]

Returns zero, although there are lines with SOME_STRING - I checked it myself))
If so:
logrt.count["/var/www/app/log/action.log"]
then it counts all lines.
If log instead of logrt:

log.count["/var/www/app/log/action.log","SOME_STRING","UTF-8"]

then he correctly considers, i.e. only records with SOME_STRING.

What's wrong?

Zabbix 5.0