Moviesheet (jpg) must be placed in same folder as movie and named as 0001.jpg to make sure it's the first jpg that the POHD displays. The movie will play when you press 'enter' button when the moviesheet is displayed on the screen. If there is no movie found in the folder it won't play.

Pressing 'Next' button will display the next folder with a jpg file (the first jpg file it finds). That means you have to have name all your moviesheets in each movie folder with the same name '0001.jpg'.

Older FW don't work with Tumbgen. The newest official 3582 will work, but is is very unstable and lots of bugs. So I suggest use the older Beta 4318 FW.

No for Mini, use back Mini FW.

are you using composite cable (yellow jack) or HDMI?

Go to Playon!HD website under 'Technical support' and read the 'sticky' thread at the top with the title "MKV file not playing information. You will find your answer there.

More and more MKV are created by the newer MKV software (which uses compressed Headers) which the POHD cannot play.

Sad to say, other Brands using Realtek chip (e.g Xtreamer) already solved the problem with their FW release, but AC Ryan as usual still blaming Realtek company instead of finding a solution   

Didn't I say to go to the website to find your answer 

There is a workaround solution available (provided by users initially). Now AC Ryan has created a sticky thread to take the credit, haha.

Just go there and find out yourself. Too much to explain here.