Resetting the CLS key fob

[DSM10000]

2013 CLS 250 model. Remained seated for 14 minutes. Both batteries are depleted and have been substituted, along with a new fob battery.
I was required to utilise the mechanical key to unlock the vehicle, yet nothing occurs when I insert the fob into the ignition. Is there a procedure to reset the fob so that it can recognise the vehicle and vise versa?

[badgx]

Has the automobile battery been completely replenished?

The fob batteries are unrelated to disengaging the steering lock or disabling the immobiliser to initiate the vehicle.

The steering lock identifies the key, and the immobiliser circuit within the key receives power through induction from a coil located in the steering lock or ignition switch.

[badgx]

http://shop.ebay.co.uk/?_nkw=car+battery&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338181132&toolid=10001&customid=2518X1570512X67bccb3714174383a0b479e18f9174b8&subId2=15

[badgx]

http://shop.ebay.co.uk/?_nkw=ignition+switch&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338181132&toolid=10001&customid=2518X1570512Xb402e73ef7c3cc64359621c48637b8cd&subId2=15

[DSM10000]

The two new batteries are completely charged.
The key fob is unable to unlock the doors, yet it can rotate in the ignition switch, although the dashboard lights do not illuminate.

[badgx]

Who replaced the two batteries in the vehicle?

Are you entirely certain that they were properly connected?
Are you certain that the protective cover has been taken off one of the terminals on the batteries within the key fobs?

Easily disregarded. Can you surmise how I am aware? 🤔

The batteries within the key fob serve to energise the RF signal for locking and unlocking. Not intended for initiating the engine.

Based on your account, it appears you might be facing two issues. I presume you have tested both keys in the ignition?

There may be a defect in the Electronic Ignition Switch (EIS), which is not unusual.

[badgx]

Can you verify the voltage in the engine compartment? Typically, there exists a Positive terminal for connecting jump leads.

[DSM10000]

The fob battery has had its protective film taken off; I am already aware of this, can you surmise how?
The primary battery and the supplementary battery both exhibit a satisfactory 12v measurement (the fob battery was also tested at 3v). I lack the means to assess the primary battery's performance under load for amperage, but that is irrelevant if I cannot start the engine.
I have additionally inspected the fuses and relays.

[badgx]

Could the wiring have sustained damage from rodents during the time it was not in use?

[DSM10000]

It is feasible, as I have encountered that problem previously, yet I cannot discern anything apparent.

[badgx]

Have you verified the primary engine ground connection and all fuses in the front and rear SAMs?

I lack diagrams of them, but it might be prudent to inspect them along with any visible wiring harnesses for indications of damage

[DSM10000]

I have observed some impairment to the loom. Previously, it experienced severe roughness, and the auto electrician discovered damage to one of the injector feeds.
I will call him tomorrow and persuade him to join us.
I appreciate your counsel.