I had this issue before and I just kept restarting osbot each time it failed and it eventually popped up without the "install webwalk" thing. Probably not the fix you were looking for but just keep restarting it and maybe that will work for you as it did for me.
DON'T take a coin less than 75m for it. I sell mine with same stats $79.99 all day
75 mage is ideal, the higher the mage the higher the combat level and the lower the price.
My non trolly suggestion is release some scripts to the community so people can get a feel of your scripting capabilities before selling an expensive private script. Work on feedback etc and it will go far, just my 2 cents