Second Product variant image in fb share is not coming
[node:field-product:1:field_images]


You'd add that in your metatag image field together with the first token that you mentioned, separated by comma.

If fb is still not picking it up, after your fetch new scrape info, try adding :file:url to your tokens. 

[node:field-product:0:field_images:file:url],[node:field-product:1:field_images:file:url]