Side by side, freezer working fine but fridge side not cold enought, set at coldest temp. Could vent between freezer and fridge be blocked?

Freezer achieving -5 is good airflow at the top is good. You have a return air problem something is blocking airflow back to freezer. Look for a vent in the Fresh Food side along the dividing wall could be as simple as product against the vent. Vent could also be behind crisper drawers. If all of that is clear Pull freezer cover and look for ice or frost buildup in vent.

The fridge gets its cold air from the freezer through a vent(damper) between the freezer and fridge.The fan in the freezer blows air through it. Make sure this fan is running. You may have to hold the door switch in for it to run. There is a flap you adjust with the fridge temp. control. Make sure it's opening and closing when you adjust the fridge temp.
The problem could be the electronic control if you have one or the mechanical linkages.

The fridge gets its cold air from the freezer through a vent(damper) between the freezer and fridge.The fan in the freezer blows air through it. Make sure this fan is running. You may have to hold the door switch in for it to run. There is a flap you adjust with the fridge temp. control. Make sure it's opening and closing when you adjust the fridge temp.
The problem could be the electronic control if you have one or the mechanical linkages.

The fridge gets its cold air from the freezer through a vent(damper) between the freezer and fridge.The fan in the freezer blows air through it. Make sure this fan is running. You may have to hold the door switch in for it to run. There is a flap you adjust with the fridge temp. control. Make sure it's opening and closing when you adjust the fridge temp.
The problem could be the electronic control if you have one or the mechanical linkages.

Make sure that the climate controls on the fridge side are set towards "coldest". If they already are, you might have a bad thermistor, which should be located behind the temp controls at the top of the fridge side.Fairly easy to replace.

the normal temperature for a refrigerator is 35-40 degrees F, so 40 at full cold setting is not correct.

If this is a side-by-side or top-freezer, make sure that the air vents between freezer and fridge are not blocked by food items or ice.

Make sure defroster operation is working normally as ice will block airflow.

Also, there is a circulating fan in most models that moves cold air from freezer to fridge. make sure that's working.

Difficult to properly diagnois with such a brief description, but try the following as a good first step at correcting the problem. Reset the freezer and fridge thermostat settings at the factory default. Also, check the freezer section to make sure nothing is blocking the cold air supply vent into the fridge, do the same on the fridge side too.

Normally is the freezer is working fine, and the fridge is warm, it can be due to either a blockage of the cold air cross vent by items in either the freezer, fridge, or both, preventing proper cold air flow from the freezer into the fridge. Also, check to see if the cold air vent is not frozen or obstructed, with a fashlight (you;ll need to remove stuff from fridge and freezer to make this possible to check.

If the vent is not obstructed and you can clearly feel cold air passing from the freezer into the fridge, it is possible that the cold air vent control has ceased operating properly and needs to be replaced. Usually though this type of problem is caused by people over stuffing things into the freezer section and blocking the cold air cross over vent. Hope this helps.

Cleaned the condenser coils which were dusty but not severely so. Checked the evaporator coils which were NOT iced. Reset the fridge to coldest setting and freezer to #5 (mid range of temperature) and waited a full 36 hours. Fridge temp is 40 F and freezer is about 0F. Not sure what is different except coldest setting on fridge. Warm weather is here but not warm enough to require AC. Temps in late afternoon in house about 77-80F. Any thoughts are appreciated because I suspect this problem is not completely resolved.

You have a defrost problem. Refrigerator gets cold via freezer. If blocked with frost, will restrict cold air into refrigerator.

Check make sure evapurator fan is blowing and nothing blocking any return vents in refrigeratro side prevent air from recirclating