Did you try giving your machine a swift kick? Won't help but probably make you feel better.

lol
Are you getting errors in the errors column?
The issue is possibly not cut and dry.
1 - go to settings >> harvester engine configureation >> import >> download default engines
try it, if it works, great.
2 - if it doesn't work then go to help >> show error log >> harvester - what are the errors?
503, 429 and 302 are all ip bans from google. With a huge pool of proxies, others can get the ips banned and google bans faster then ever these days.
3 - are you using advanced operators or queries? Try some basic queries as a test, like
car
cloud
green
etc...
do those work?
4 max out your proxy retries under settings >> connections timeouts and other settings >> more harvester options - proxy retries.
5 - wish this wasn't the case, but google has started the dreaded splash screens like bing and yahoo in some locations. Forcing you to accept tos service/privacy stuff before you proceed and scrapebox can not get around these. You will know this is the case if you follow the above and you get zero results, but there are no errors in teh errors log/errors column when harvesting.
You need ips from a country that doesn't have laws that require these types of splash screens. Think GDPR and similar, Ive noticed it for many countries in Europe and around and some countries in South America, but there could be others.
6 - If you made it thru 1-5 give your self a pat on the back for good effort and stick with it, you will get it.
Edit:
7 - something else you can try is go to settings >> harvester engine configuration.
the click google and at the bottom there is a test engine button and also an option to add in your proxy. So put in the rotating proxy gateway.
do the test, if it fails, save the raw html. Do that a half dozen times. Don't worry about if it works a couple times, we are looking for the failures here.
then open that raw html in a browser. What do you see?
Is it a lot of pages that have like a blank white square in the center of the page, possibly with a spinning circle still loading type thing? This is the splash page I was talking about
or is it a page that says there is bot traffic or similar?
or does it look normal? Because its possible your getting some ip from like malyasia or wherever (doesn't matter the country, just picked on at random), that is redirecting to the local google and that google has different html. Thats not typical for google, but it is possible. Worst case send these tests to support and they can tell you more if you can't sort it.