The LP file format is not standardized. For example, some solvers, including Gurobi, require spaces between variables, coefficients, and operators in an LP file. That is, the constraint \( x + y + 2z \leq 2 \) must be written as x + y + 2 z <= 2 in an LP file.
If Gurobi is unable to read an LP file written by another solver, try writing the model file in the MPS format instead.