Can I pick-up my capital loss on my 2021 form as reported on my 2019 return, if I did not claim it on my 2020 short form?

[ColeenD3]

No, you can't skip a year and then resume with the original loss.

If you have unused capital loss carryovers, you need to go back through the years you didn't take them and reduce the carryover amount by the amount allowed in those years. In other words, you have to take them each year as allowed, you can't just skip a few years and then use the available loss from the last year you used them as the balance allowable in the current year.

[Hal_Al]

Q.  Can I pick-up my capital loss on my 2021 form as reported on my 2019 return, if I did not claim it on my 2020 form 1040?  

A.  Simple answer: No.

But taxes aren't simple. So, it depends on whether it would have changed your 2020 return, if you had properly filed it.  

Basically, you are allowed to use your standard or itemized deductions to reduce your taxable income before having to use your capital loss. Technically, if your standard (or itemized) deduction was greater than your AGI, without  the capital loss, then all your capital loss is carried forward. So, look at your 2020 tax return. If line 12 was bigger than line11, all of your 2019 capital loss will carry forward to 2021. 

If, not, you'll have to recalculate the 2020 carryover, and maybe even file an amended 2020 return.