Do not force it. Ice can hold the flap while its plastic hinges and catch remain fragile, so pulling harder can break the fitting.
What the observation tells you
The appliance may need the model's controlled defrost process, with food protected elsewhere first. A knife, screwdriver or direct heat source can damage the compartment or concealed cooling parts. Melting only a small visible edge may not release the rest safely.
A useful next step
Follow the exact owner instructions or obtain advice if they are unavailable. Explain where the ice is holding the flap and whether it followed a closure problem. Do not chip at the liner.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.