Without more details or knowledge gained by experience, it's impossible to answer your query, unless using special circumstances such as ultrasound, the concentration of water must be effectively zero, as water will cleave the Grignard reagent
Some Grignard reactions are far harder to start than others; if you're using an ethereal solvent then the percentage of water present must be below .01%
You could try flame drying your apparatus, and a test tube, then attempt to start the reaction in a test tube with the reagents in the same proportions. If it starts reacting, then measure your reagents out and put them in the reaction flask, then add the contents of the test tube, which will initiate the Grignard reaction