This is an exact clone of ZBX-130, which has already been solved in 1.4.3.

Could you please provide information of what is not working properly and in which versions?

Affected version: 2.2.2

Initially wrong configured log[] or logrt[] item never become supported. Only one way to fix it - recreate the item from the scratch.

What was the reason the items became unsupported? What is it a non-existing log file, wrong regular expression that did not compile, or something else?

The reason was in forgotten marcos for host.

logrt["{$LOGPATH}","{$STRING}",,10,skip]

And mentioned item didn't became supported after adding the marcos.

Could you please check whether your issue is the same as in Oleksiy's comment at https://support.zabbix.com/browse/ZBXNEXT-444?focusedCommentId=72496&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-72496 ?

I guess Oleksiy's issue is not my case because the item did not become supported after {$STRING} match.

You are running version 2.2.2. Is it the version of both the server and the agent? Are you using a proxy?

Zabbix server v2.2.2 (revision 42525)
Zabbix Agent (daemon) v2.0.6 (revision 35158)
The host is monitored without proxy. Actually we also have proxies the same version as server.

I have tried reproducing the issue using the versions that you specified and by using the following scenario:

1. create empty file /tmp/logfile.txt;
2. create item logrt["{$LOGPATH}","{$STRING}",,10,skip];
3. wait until agent starts saying that it is unsupported:

    31118:20141008:162611.711 filename '{$LOGPATH}' does not contain a valid directory and/or format
    31118:20141008:162611.711 Active check [logrt["{$LOGPATH}","{$STRING}",,10,skip]] is not supported. Disabled.
   

4. define macro {$LOGPATH} to be "/tmp/logfile.txt" and {$STRING} to be "string";
5. wait until agent stops saying anything about the item;
6. append "string" to /tmp/logfile.txt
7. wait until data is transferred to the server.

At this point I see in the frontend that the item is supported.

Could you please provide the exact steps to reproduce the problem?

It seems that I've created two items who checks the same log file and one of them stay unsupported all the time. My fail.
Anyway, after logrotation the logrt item become unsupported until found {$STRING}.
So, it's issue described in ZBXNEXT-444

Thanks for clarification, I really appreciate your help.