(1) Explain your problem, don't simply post "This isn't working". What were you doing when you faced the problem? What have you tried to resolve - did you look for a solution using "Search" ? Has it happened just once or several times?
(2) It's also good to get feedback when a solution is found, return to the original post to explain how it was resolved so that more people can also use the results.
Highest negative number may not solve your problem as real critical activities may have FT with less negative number.
For effective project management you need to be able to identify REAL critical path.
I have offered a solution in this post:
https://saluteenterprises.com.au/total-floats-with-or-without-project-de...
Regards,
Alex Lyaschenko