This is either a disc in the navigation system problem, or navigation disc reader problem.
Navigation disc reader problem is more likely cause. If what I suspect is the cause of the problem Navigation DVD unit from the boot needs to be taken out and inspected at repair shop to see if it can be repaired or needs to be replaced with another one of the same kind.
There is no Disk on the car when I got it. It came with SD Card inserted it was working fine but when I changed the battery it stopped working after that. Here is the image for that.
Is there any other way to fix it without going to mechanic.
I can't add anything about Sat Nav DVDs.
My 1999 KV6 came with a GPS cd reader in the boot. CDs may be found on the web but the last issue was made in 2014-2015.
Anyway as @Roverlike told you it's likely that some serious mod was made in your car: never it has had a sd card.