Indesit wie167 issue taking off filter cap

[Raspberrydesigns]

Indesit WIE167: it's displaying a f05 error code, stopped with water still in it. We took the lower front plate off and drained the water out. From what I've read elsewhere, it's been suggested that this black cover comes off and to clean the filter inside and check for blockages. The black cover turns only a quarter anticlockwise (ie 12noon to 9) and doesn't seem to come off. I don't want to force it and do more damage if indeed it doesn't come off. The manual I pulled up from indesits website suggests that it does. Does it turn further anticlockwise or do I need to encourage it off with a screwdriver? Please help. I don't want to call someone out if I can solve it myself. Thanks eversomuch.