Milko It’s a simple John guest type fitting, I doubt it’s seen enough use for the o ring inside the fitting to have perished.
press the fitting in (I don’t think it’s pull) at this point
Then pull the tube out and reinsert it fully. If it still leaks, pull it out, inspect the end, if it all looks good, no scratches or damage, then make sure it’s clean and pop a vit of vaseline around it and then reinsert it. You don’t need loads and the internal teeth that grip the pipe should grip through the vaseline.