I have followed & understand the instructions re home button & the sleep button but nothing happens
Hi, welcome to iPF!
First of all try this:
Restart your iPad - turn it off and on again.
Reset it: press and hold Home and Power button until the Apple logo appears.
Close apps: double tap Home button to reveal the multitask bar, delete all apps there.
Perhaps it's possible then to take screenshots (short press Home and Power button at the same time).
If this doesn't help, take a look at your Settings. If there's a profile (Settings - General), perhaps an app disables screen capture. In this case you have to remove the profile to enable screenshots again. Deleting the app won't help.
One suggestion, if this also doesn't fix your problem: use Assistive Touch.
Go to Settings - General - Accessibility - Physical & Motor, Assistive Touch, enable it.
A button in one of your iPad's corners will appear. Tap it, you'll see this:
Tap "Device".
Now choose "More".

Here you can make a screenshot.