Agree. Fix-A-Flat and like products will damage the TPMS. Is this happening on more than 1 of the tires? Could be that the tire is defective or unsealed from the wheel. My advice would be to first have it checked at a tire shop. Hopefully, nothing is wrong with the wheel and/or that you won't have to replace any of the tires. Hate to say, but occurrences like this are one of the reasons I have always just gone ahead and purchased the hazard insurance.
2011 Panamera 4S...GT Silver / Espresso
2013 Porsche Carrera 4; 2012 Mini CooperS
convertible; '04 GX470
Prior BMWs: `05 645CiC; `07 650i; `08 M6 convertible; '08 135i; `11 750ix MSport
"You think that's air you're breathing now?"