Have mercedes E class key fob will not open doors,

Most manufacturers will install a cable in the trunk on the fill side to pull for manual release. It may be in sight or possibly behind a panel. Owners manual should give instructions as well

May be a blown fuse or bad connection, Check for voltage at the boot latch.

Hi, if all of the locks on your Mercedes fail to open (or close) first check your key fob to make certain that its battery is working. Replace the worn out battery, if necessary. If key fob is working, you may have a faulty key fob, which can be repaired or replaced by taking it to your dealer.
If just one lock won't open on your Mercedes, then the problem may rest with broken wiring, a bad solenoid, or perhaps with a blown fuse. Check your fuse box first to determine if a blown fuse is keeping the lock from working. If so, replace the fuse.
You likely have a shorted door lock actuator, which you can replace with a new unit for the lock that is not working. If a door unlocks, but will not lock again, then replace the door switch.

Besides there is not OBD II 888 code, i have never heard or seen it before...

SOUNDS LIKE A BAD KEY FOB..BUT BEFORE YOU GO WASTING ALL YOUR MONEY ON ANOTHER ..TAKE THE BATTERY BACK OUT LOOK INSIDE WHERE THE BATTERY SITS AND MAKES CONTACT..ARE THE LITTLE CONTACTS TOUCHING THE BATTERY

try this

open it from inside by dropping the back seat if possible

The fob and car have to go to the dealer to have it reprogramed.

Your FOB may be programmed to press once to open the driver door, press twice to open the rest. This feature is to prevent uninvited guests jumping in the car when the driver getting inside the car the same time.
Check out the FOB key setting.

The factory wireless key fob has a "mechanical" key embedded in it. Slide the lock tab to slide the "mechanical" key out then use it to unlock the driver's door.

hi,try your spare key