Has a tech positively identified the actual leak location with fluorescent dye to make sure it is not a mis-seated connection or o-ring or vibration induced crack ?
The filling valves are a very common weep point, especially if uncapped or missing cap o-ring.
They do state that if the dye is visible, the hole is too large (q&a on the Amazon listing) for the product to work.
I have had rubber hoses that turned fluorescent after a few days when i could not otherwise sniff a leak.
My grandfather was a commercial A/C tech and hated the stuff . Clearly, it works for some. I suspect that if you have to open the system in the future, it would have to be flushed clean to remove the residual unreacted additive in addition to the usual vacuum pump out drying and leak test. And pulling a full vacuum may dislodge the plug.
just a few thoughts.