Tubeless leak around valve stem. Would sealant likely fix?

[makoti]

Had a set of wheels that worked well, until the front developed a braking issue I think was due to sealant build up. Went ahead and replaced the tire, since it had a lot of miles on it. Switched to a Fillmore valve.
Well, I couldn't get a seal around the valve. Tried several times (NO SEALANT YET), retaped twice, same problem.
So I switched valves to something else, an American Classic I had laying around, retaped again. Same, though not as pronounced, problem. Still leaks from the base of the valve, but not gushing out. I haven't put back in the old valve yet, thinking new would be better, but I guess that will be the next step.
Question is: This is without sealant. Would sealant seal this up? I've never had this issue before. Leaks, but never the valve. Sealant would take care of most of those. Any thoughts as to why the rim suddenly won't seal the valve?