Solve block

The guesses you provide yield a non-real result.

Try to choose guess values which make the expression you want to be zero a real value.

Or, if appropriate, you may use the absolute value:

Furthermore I would suggest that you define a function for the constraint

and use this function in the solve block and to check the result:

Of course you cannot expect a unique solution - you provide just one single equation but have eight variables to jiggle around!