Since a few days ago any filter code causes the message "The filter did not match this change." when testing a filter against a change.

Go to a page like
https://pt.wikipedia.org/wiki/Special:AbuseFilter/examine/log/2148379?testfilter=true&uselang=en
and type any code, e.g. true, or 1, or 2>1. Any code causes the same message. No code matches the edit.

The following API calls produce the output

{
    "abusefiltercheckmatch": {
        "result": ""
    }
}

https://pt.wikipedia.org/w/api.php?action=abusefiltercheckmatch&logid=123456&filter=true
https://pt.wikipedia.org/w/api.php?action=abusefiltercheckmatch&logid=123456&filter=1
https://pt.wikipedia.org/w/api.php?action=abusefiltercheckmatch&logid=123456&filter=2%3E1
while the calls to
https://pt.wikipedia.org/w/api.php?action=abusefiltercheckmatch&logid=123456&filter=
https://pt.wikipedia.org/w/api.php?action=abusefiltercheckmatch&logid=123456&filter=false
https://pt.wikipedia.org/w/api.php?action=abusefiltercheckmatch&logid=123456&filter=0
produce this:

{
    "abusefiltercheckmatch": []
}

The extensions code test for data.abusefiltercheckmatch.result in JavaScript:
https://github.com/wikimedia/mediawiki-extensions-AbuseFilter/blob/727a93708505aba6a1271430f783b02d58436079/modules/ext.abuseFilter.examine.js#L54
so it is likely that previously the API was returning something different from the empty string '' when there is a match.