Lenovo Thinkpad T520 Function keys not working

We are having a fleet of T520's that is completed with the BIOS upgrades and the existing version is 1.26. After upgrade, I found that the functional keys (From F1 to F12) are not working. I tied to press them harder but that was not working. I have tried to press them while boot time but that is not working at that time also. The only technique we have had success getting to the BIOS is through pulling the CMOS battery out and after that flushing power out of system and afterward booting in. We will obtain a BIOS Date/Time error after this and we are provided with the option to bounce through Pressing Enter otherwise pressing F1 to enter into BIOS Setup. This is the only way by which I will be able to get into the BIOS and that is just by pulling the CMOS battery. If you have any solution for this then please let me know that. Thank you so much in advance for reading and replying to this.

You have not specified that if the problem is with the cold boot or the warm boot or with both of them. I have seen many of the cases where functional keys are working some of the times when you do the warm boot but they will always work when you do the cold boot. This is the only thing that I can suggest you for the time.

I can also say that T520 BIOS is really bad. I initially booted the machine and enter to the Lenovo factory load therefore I will be able to run the asset info program as of the Lenovo, Everything went well, afterward I rebooted and after this permit the machine communicate to server to load it's mac info within the server. After doing this, I rebooted once more and the thing went to pieces. I tried by pressing the blue ThinkVantage button but that also does not provide me any option.

The only solution I have for you is to turn off the computer and then turn it on back and keep on pressing the F12 button constantly. See if this can let you to the BIOS settings.

There might be some problem in the keyboard. Try to connect some external keyboard to that and see if that is showing you the same thing. If it is working well then the problem is with the keyboard and you can have a talk to the Lenovo support and they will tell you that what is the exact problem with this and how this can be resolved.

Lenovo support is the only place where you will get the solution for this.