I see how it looks like they stopped in 2018, but you might at least contact PSU Math. Call the department secretary and ask for a point of contact. Perhaps they are still running it, after all there's still an application form on their website. Also, note that MASS runs in fall, but PMASS runs in spring. So if they are running PMASS, still, that would be ideal for your student. In addition to confirming if they've stopped MASS/PMASS, they might have a suggestion for an alternate for your kid (if they have stopped it).
I did a search for math semesters or years or summer programs and there wasn't much (some stuff in Budapest and Moscow):
https://maa.org/member-communities/students/semester-and-summer-programs
The no such agency also came up as a sponsored link, so you could get the kid to look into that. https://www.intelligencecareers.gov/NSA/students-and-internships?gclid=Cj0KCQiAuqKqBhDxARIsAFZELmKfVXIZDMveZ7gh-ejRG-gqJA1GPZ62OkIH10FDcA37Y2IldHN_swMaAky1EALw_wcB (bunch of options, so weed through it and probably have the kid contact them for more details).
Slightly joking, but kid could maybe double dip and sign up with NSA and have them pay to send him to Moscow math program. Hmmm... ;-)