Add fillers or additives after resin and hardener have been thoroughly mixed See Mixing in the User Manual. Do not apply additional material over non-curing epoxy. See epoxy removal note in the user manual. Check for proper resin and hardener. Resin will not cure properly with other brands of hardener or with polyester catalysts.
Insufficient cure See above.
Wet out bonding surfaces and apply thickened epoxy. Re-wet very porous surfaces and end grain. See Two-Step Bonding in the User Manual. Contaminated bonding surface. Clean and sand the surface following the procedure in the User Manual.