First off, clear all model setting to make sure you are starting fresh.

Set up your first model, making sure to set the modulation to FH4T, and the Safety Link to 1 (in bind menu), bind the first receiver.

Now switch to model 2, set modulation to FH4T and the Safety Link to 2,(in bind menu), bind second receiver.

If it still does not bind, would suspect faulty Rx. (Also check condition of antenna, should have a silverish/clear tip 30.5mm long exposed from black coax. if it is damaged, it may not be receiving. You can buy new antenna's for these)