So sorry to hear you are having this problem,
general guidance here is to do the following [only once] use the 'audio preference' in the pre-meeting [or after you've joined] to ensure that Webex is choosing the correct system mic, once selected we will 'remember' this setting
Then make sure 'automatically adjust volume' [enabled by default] is checked, which will help with getting the mic sensitivity right automatically as you are speaking.
Also consider enabling 'remove background noise' in the audio settings if you are in a noisy environment/working from home. This works fantastically to eliminate even the loudest environments.
Finally, if you are inserting a 'music' source /multimedia into your mic, enable 'music mode' to allow the Mic to passthru the high fidelity audio without any of our background audio detection/automatic gain control for the best experience.
Last but not least, the Focusrite scarlett 2i2 has [2] XLR audio ports, and Webex does not recognize the 2nd port, so for Webex [and S4B, and a few others], make sure to use Mic 1 although I imagine you already knew this.
Also, if this doesn't satisfactorily solve the problem I would suggest a call into our worldwide TAC organization? I quickly reviewed a summary of prior cases referencing this product and it appears they were all solved via a variety of methods. If Webex isn't recognizing the device while other applications are we would love to get a log of this [our TAC group is great at helping with this] 1-800-553-2447 or on the web
