Purchsed a used Sigma 105mm F2.8 EX DG HSM off eBay. Research says that it should fit the Canon SL2. However, the lens will not turn to lock in. It does fit snug into the mount, just doesn't turn. On inspection the lens is super clean and I don't see any damage around the mount area. Thoughts? Want ot make sure I'm not missing something before requesting a refund, thanks.
Make sure that you have a Canon EF mount by comparing the Sigma to another lens. One quick test, which is not very informative, is to try to mount a Canon lens capo onto the mount. If the cap does not iit, then you may have the wrong mount.
Otherwise, get a refund. Did it come with a hood and case? This issue just might be the tip of the iceberg. In fact, I would be inclined to get a refund, anyway. While there are good deals to be found on eBay, it is not where I would shop. I do not think their return process is worth the hassle.
Sigma makes their lenses with several different camera mounts. You need to confirm that it is in fact a Canon mount. One problem with off brand lenses is tolerance stacking. Sometimes a mount can be tighter that average but still work. It should never be really hard to mount or feel like it has hit something solid.
Sigma used to offer, perhaps they still do, a re-mount service for some of its lenses. This is because the lens itself is the same for any different mount. And, as far as I know there is no outward apparent difference distinguishing which mount it is for.