You look at the Instructions and in the Box 12 Code descriptions, it says:

"Elective deferrals and employer contributions
(including nonelective deferrals) to a section
457(b) deferred compensation plan".

Employer contributions and nonelective deferrals don't qualify for the credit.  Even if ignore the "employer" part, nonelective deferrals do not qualify for the credit [see §25B(d)(1)(B)(ii)].

https://www.irs.gov/pub/irs-pdf/iw2w3.pdf#page=32