Angy, exchange R5 and R4 in order to get a gain of 3.
At the same time - to ensure a safe start - make R5 a bit larger (20.5 kohm).
The diodes remain where they are (across 20.5 k)
Sorry - I was confused. My above comment does not apply. I had overlooked R1.
However, R4 seems to be too large. Reduce it to 1...2 kohms.
More than that, for simulation purposes (to start oscillations) you should
* either switch-on one or both power supplies at t=0 in transient simulation
* or give one of the capacitors an intial condition (IC with some millivolts)