I didn't run the code and so don't have an output to share. Of course the expression may not be analytically solvable for epsilon. Looking at your expression, it appears to be the difference between the ratios of two quadratic expressions in epsilon. So it is likely to be a quartic equation when expanded out. The solution to the general quartic polynomial is quite a mess, and the coefficients of the terms in the original quartic are very messy--so your final result will be a very large expression. Perhaps you want to take a different approach to whatever use you are planning to make for this?

Your code has a mixture of StandardForm and TraditionalForm content mixed together. Because of this the syntax highlighting is not showing the bracket mismatches. Click on the cell bracket of the cell with your Solve function to select that cell. Then click on the menu item Format>ClearFormatting to remove the mixture of formatting. When you do this you will see where there are unmatched parentheses (they will be colored pink) and then you can figure out where to add or remove parentheses to produce the expression that you need to work with.

I hope this helps.

--David