1. Check in the file /etc/dpi/fastdpi.conf parameter black_list_sm=1 ?
Yes - SM is activated. Blacklist is activated by service activation for subcribers.

2. On test subsriber check that service is off:

fdpi_ctrl list --service 4 --ip 192.168.1.60 
1/0/1 - service is off
1/1/0 - service is on
Result processing ip=192.168.1.60 : 1/0/1
- service is off

3. In the config file /etc/dpi/fastdpi.conf sets IP of subscriber with blacklist is deactivated:

trace_ip=<IP>
after it:
service fastdpi reload

check for test URL:
grep -A5 metfen fastdpi_slave_?.log
or
cat fastdpi_slave_?.log | grep metfen.com -A 5

HTTP_HOST=_metfen.com_
HTTP_REFERER(0)=_null_
HTTP_USER-AGENT=_Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) 
Chrome/43.0.2357.65 Safari/537.36_
HTTP_COOKIE=_null_
[TRACE   ][001693490086826396][2888570700] CHECK_HTTP : URL=_/_
      HTTP_HOST=_metfen.com_
      HTTP_REFERER=_null_
      blocked=0
      new_prg_id=0
      
in log blocked = 0 no redirection, new_prg_id=0 subscriber has no service is on.
No active blacklist for the subscriber in the VAS Experts DPI.

4. Dump browser session with fiddler for blacklist URL if redirect is still active then check your redirect page for folowing instructions:

Cache-Control: max-age=0, no-cache, no-store, must-revalidate
Pragma: no-cache