That OTG checker app is only going to confirm whether your tablet does or does not support OTG. But that's only one aspect you have to take into consideration. The OTG cable or adapter you have might be the problem as not all brands or models will actually be compatible with your tablet's OTG capability. Plus it's a matter where even when your tablet support OTG and your OTG cable/adapter is compatible with your tablet, that does not mean that external USB device you're trying use is compatible with your tablet.
So in your instance there's a chain of variables to consider -- the tablet, the OTG cable/adapter, and the DVD drive. Unfortunately you need to go through an arduous process of trial-and-error to see what does and what does not work. As
@mikedt referred to, can you successfully mount something like a USB thumb drive or an external hard drive to your tablet via USB? If yes, than that indicates your OTG cable/adapter is compatible with your tablet. If not try more than one external drive because while most will be, some won't. If you can't eventually get your tablet to detect an external drive, assume you do need to find a replacement OTG cable/adapter that's a different model, or even brand.
Once you've confirmed your table and OTG cable/adapter are compatible, that leaves the DVD player as the problem. If you did have to get a different OTG cable, that itself might be the solution to the problem. If not, it could be a driver issue.
With a PC, you might need to just install a device driver or some software to be able to use an external DVD player. Or when you plug it in, that prompts the OS to automatically load its existing device driver. But with Android when it does not occur automatically in the background, it's not a matter of manually installing a driver, that's something done by installing a manufacturer-supplied app. It's the app that contains the necessary driver/firmware. So check in the Play Store if the manufacturer for your external DVD player has an app and hopefully that solves your problem.
