I do not understand what this sentence means. Neither English nor Romanian.
I think it's an attempt to tell someone not to work because it's a strike.
What's a difference between lucru and manca?
muncă means physical work.
lucru means work like in an office etc.
For example: you work as driver to bring people from the airport to the city. But there is a strike at Wizzair...so you don't have work during the strike. ;-)
Is "Fără slujbă în timpul grevei!" wrong?
Not grammatically, but the meaning it's weird: like an orthodox priest saying that...
... and again a strange sentence
Why not: " Fără serviciu în timpul grevei" ?
This is like saying you lose your job during the strike... Fără serviciu=unemployed