I have had two know synopie and possible another one. One 2010 and one 2011. And one 2012. Doctors can't find anything so far what could cause this?

Many possible causes. There are many possible causes for fainting with postural collapse and loss of consciousness, including vasovagal reaction, orthostatic hypotension, cardiac arrhythmia, hypoglycemia, neurological problems, such as seizure (can be mistaken for a syncope). It would require a thorough history, including your medical history and meds, physical examination and appropriate tests to determine the cause.
Syncope. I do not know what tests were done. Common causes include sudden drop in blood pressure which may be diagnosed with tilt table testing, heart rhythm problem that may require 24 hour monitor or 30 day monitor or implantable loop recorder or evn electrophysiology study. Or it could be a seizure that could be purvey of neurologist.