I need to make up some leads.
By the sounds of it you have taken the panel to the store and tried inserting the loose connectors in the panel socket. They will be very difficult to insert as the connector hasn't been crimped yet, so the gold contacts not being pushed in are what is making it difficult. Only after they are crimped and the contacts pushed in/down onto the wire would you be able to insert the connector properly.Thank you, have crimped a cable and it is fine. I had one premade lead that was near impossible to remove, so I didn't want to get caught out,
Also make sure you get the connectors suited to the type of wire you are using. There is a difference between connectors designed for stranded or solid core wires. If you mix it up, you will still have the same issues you are experiencing now.