Help! Cant run after update. Vulkan Support???

I'm getting the following message after updating ESO. 'ESO cannot start because your machine's Vulkan support is either insufficient or nonexistent.'. I'm running a 2011 iMac:

3.4 GHz Intel Core i7
AMD Radeon HD 6970M 2048 MB

I've tried all 3 options but nothing seems to do anything.

If anyone could help it's be much appreciated. Google doesn't illuminate.

Pb