Im trying to connect my CDTV to a modern LCD tv with SCART cable...

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I'm almost 100% sure you don't have enough voltage on blanking pin 16.

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How can i fix it?

you need to provide above 1  and below 3 Volts on pin 16, on TV SCART socket.
usually, people use simple voltage divider, with resistors. Amiga video socket has both +5 and +12 Volts, so you can choose, but be careful.
I'd first check the cable if it already has something on pin 16.
 

its used to automatically switch TV to RGB (component) instead of CVBS (composite).
older TVs didn't need it, as you could select RGB with remote.
perhaps you're lucky, and can select it with remote too, check TV manual.

here is a nice explanation of blanking signal:
http://www.worldofspectrum.org/forums/showpost.php?p=717712&postcount=8

oh, there is a possibility that your TV simply doesn't have RGB SCART, only CVBS.
if so you're SOL.

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looking inside the connector, there are no connections to pin 8 or 16 in the scart end.
inside the db24 connector there are no connectivity to pin 22, not even a hole for the connector pin.

in other words, i need a new scart cable...

well you could modify that one, provided it has enough wires. or perhaps borrow one from audio if tv is not stereo. also sometimes it has multiple GND wires.

by component, you mean YPbPr? Amiga has only RGB component out, you'd need 'complex' adapter to connect it to YPbPr.

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so, you are missing pins on 23DB connector? they are hard to find, people usually hack the 25pin.
3 wires is more than enough, you just need couple of right resistors, depending which voltage you choose. there are schematics on net.
forget YPbPr, it is not worth the hassle or money.

if you never soldered before or don't have a friend who does it, I'd just buy another cable, they should be cheap nowadays. ask seller for schematics or some guarantee.