7-Pin Plug Hard to Connect. Is Dielectric Grease the Answer??

@andyboy - tight is right?  Our 7 pin goes in easier by tipping it up and leading with the lower end.  Kind of hard to describe.

@andyboy - correct.  Ours is mounted so that it faces inward toward the license plate and it can be a challenge, so I am empathetic😊

Dilectric grease should not be used on the connector terminals. It is not conductive. Connector plugs are designed for a "bare" contact. Connectors should not require any lubrication in that they are designed to self lubricate. Dilectric grease could also carry dirt into the connectors. 
It would be appropriate to use it on the outside of the shell to help you insert/remove it (and keep water out) but do not get it inside the plug.
If you think you have a connectivity issue a product like Tweak is designed for improving contacts connectivity but based upon your explanation it sounds like a fit/alignment issue, not connectivity.
You might want to check the alignment tab on both sides of the connector to see if there are burrs or damage that are keeping the plug from fitting.

We use the dilectric grease to protect the 7 pin from corrosion and water effects, too.  This is the first time I have heard not to use it that way.  Found this info on theDrive.com.

Will Dielectric Grease Worsen a Connection?

There is a myth floating around that putting dielectric grease into electrical connections can cause them to fail because the grease gets between the metal. That’s not true. 

Although the dielectric grease does insulate the metal and wiring from external invaders, the contacts are tight enough to still maintain a connection, the grease is just displaced. That said, you do not need to squirt huge globs of dielectric grease into your connectors as you see in some videos out there.

When To Use Dielectric Grease

Dielectric grease acts as a lubricant, a sealant, an insulator, and a protectant when lightly used on these applications.

• Battery terminals
• Spark plug boots
• Bulb sockets
• Trailer connectors
• General electrical connections
• General plastic or rubber lubrication

Use electrical contact cleaner for your electrical part of the connection. You can use it to clean both the male (tow vehicle receptacle) and female (camper power plug). Use silicone lubricant on the the non electrical part (outside) of the connection (part that goes in the channel - that may be what is binding). Like previously mentioned, dielectric grease to protect a connection not improve it - it's not conductive. But if it's something you tighten like a battery terminal it will force the grease out as you tighten it. Here's an example: clean battery cable and battery terminal with electrical contact cleaner. Connect cable to battery. You can now put dielectric grease over the connection to protect it from dirt and other contaminants. I use a battery protector spray instead of dielectric grease for that purpose. On my TV and camper connection I just clean periodically with electrical contact cleaner.