Lens stopped working after holding lens when on auto focus

Sure you did not switch to manual focus while testing the Tamron? Sure all settings are correct?
If the Tamron still auto focusses on you 7D, check the forums about this. I know Nikon sometimes messes up the firmware, when a non Nikon lens is used, but not on all camera's. And not with every firmware.
I don't know the 7D enough to check more details, but check everything about the AF settings. I can't imagine your lens did something wrong with the camera.

its not possible to use the lens with digital camera .........but can you be more specific about the digital camera with which you are trying to use the lens

Did you switch the AF / MF switch to AF (Auto Focus)?
It is on the lens.

Try cleaning the contacts on the camera body and lens where they meet with a cotton swab lightly dampened with rubbing alcohol.

If it's only two months old then it's still under the manufacturer's warranty so send it back to Tamron. I can't tell you where to send it as you haven't said which country you're in. Tamron value their reputation and usually provide excellent after-sales care.

If you're in the UK you additionally have Sale of Goods Act protection for up to six years in England and Wales and five years in Scotland. Either way, the Act allows you to demand a full refund or replacement from the retailer; I'd suggest a refund as bad lenses often come in batches and a different supplier is less likely to have one from the same production batch.

Note that any attempt to fix the lens other than by normal use of the lens and camera controls may completely remove your warranty benefits or consumer protection.

Could be that the electrical contacts on the lens / body need gentle cleaning - try that.

Make sure your AF-switch on your camera and your lens are both turned on.

Tele convertors on their own do not focus - that is achieved by the lens. Are the lens contacts clean and correctly aligned with those in the camera ?

if it is an auto focus lens that works on one eos camera, it should work on almost all of them. the only known exception is that some high end extenders will not fit the eos1dmarkII as it protrudes into the opening too far.
but a good rule is that if it fits without any obstruction issues, it should work. try cleaning contacts on the lens and camera body. if that doesn't fix it, talk to Tamron. you can use it manually, but will not be as easy and you would get less predictable results.

my suggestion is to always go with lens from camera maker.

sounds like there is an issue with the tamron lens. not the camera.
good luck
mark

This is usually a torn flexible circuit or binding aperture in the lens. It'll have to go to a repair shop for replacement. About a $80 job.