Unknown disc on philips ht9150/98

I have a lesser Philips system and have run into this error, there are a couple of things that can cause this that I know of:

Dirty discs can be misread. I usually just run it through water and wipe clean with a cotton rag to see if it helps.

If you player is only for DVD, it will not read Bluerays.

If the disc is a DVD, check the region. I have read some players will detect all regions, but many will only detect region 1 (United Stated).

Another possibility is NTSC versus PAL. You will find NTSC in (United States), but if you buy you disc online / used, it could be Pal.

Lastly, If these are not the cause you might want to try updating the firmware, Philips is pretty good about providing updates on their website. Come to think of it, the original problem I had with this error went way after one of these firmware updates. I thought the error might have been heat related, but has not come up again since.

Did you try another disc?
Try other discs - preferably store bought. If it will not recognize store bought discs then you have a defective unit.

Is the "unknown" disc home made? could be that the homemade disc has not been created properly or is a type of disc that the unit cannot read.