Recapturing status of h1b ( before the 6 years, status expire)

I have a query regarding the h1b visa. So, my husband’s h1b visa got approved initially from 10th Oct 2015. But he landed in the US 26th Dec 2015 and started his working officially from 27th Dec 2015. Then after 3 years, when we filed our extension, we got our visa rejected and we came back to our home country on 25th Jan 2019. Even we filed the petition again in India and it got approved in march 2020, but due to covid we didn’t get to stamp the visas. Now, we are worry about the recapturing time of h1b, as I heard that, the h1b visa holders suppose to be claim their recapturing time before the h1b visa status over of 6 years (Means During the status of 6 years of h1b visa valid from Oct’2015 to OCt’2021). Please clear me on this, that if in case we will not be able to make it within this duration (From valid date to expire date) back to the US due to covid or any other reasons. Does my husband is losing his visa and he will not be able to claim the remaining cap of h1b.

The 6 year rule is not valid anymore. It used to be that way.
Once you have got your H1B, you can use the total 6 years anytime, there is no time bound. You can read all about it in below article with official references