Changing frequency of 555 timer with varicap or capacitor
If you did everything well then the frequency does change but the change is so small that you don't notice it.

What Varicaps are you using?

I bet that their capacitance varies between say 10 pF and 200 pF.

So how much would that make the frequency change?

When the varicaps are at 0 pF, only the 10 nF capacitor is there determining the frequency.

When the varicaps are at 200 pF, combined with the 10 nF capacitor you would get 10 nF + 2 x 200 pF (2x since there are 2 varicaps) = 10.4 nF

That's a difference of 0.4 nF on 10 nF which id 0.4/10 x 100% = 4%

That's too little difference to notice.

To make the difference more noticeable you would have to lower the 10 nF in value. You could lower it to 1 nF resulting in about 40% frequency change. That should be noticeable but it's probably still not what you want.

You cannot go much lower than 1 nF as the 555 chip simply isn't suitable to work with such low values.

You really should be looking at a different way to change the oscillation frequency of a 555. There are plenty of examples to be found if you look for them. Google for "555 VCO", VCO means Voltage Controlled Oscillator which is what you're trying to make.