Seems a simple plumbing issues - case of a blockage or another leak..
Bare in mind that if the pipe still contains fluid, you might not hear or feel much sucking of the pipe until the fluid in the pipe has all been sucked into the manifold.
When blockages / leaks are sorted, Flashlube might just want adjustment to start dripping again.
Full time LPG installer
Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
2 miles A1, 8 miles M62, http://www.Lpgc.co.uk