XPS 15 9550 - TPM has "disappeared"

Call Dell -- the mainboard will be replaced under warranty.

I had the same symptoms when upgrading from 1.1.15 to 1.2.0 and the only way I could resolve it was to:

1) Enter the recovery and back up everything you need (i.e. prepare for a fresh install).

2) Roll back to the old BIOS (for me it was 1.1.15) - which should make your TPM re-appear.

3) Re-install a fresh copy of windows.

4) Upgrade your bios to the latest version.

5) Check that the TPM can still be seen.

6) Encrypt again.

It worked for me and might work for you. I just hope I don't have to do it for every BIOS update!

Thanks for your reply. I'm actually having a hard time locating the previous BIOS versions, any suggestions? The support page for the laptop only lists the latest. 

This just happened to  my XPS 15 9550 as well.  I had BitLocker enabled using the TPM since June 2016.  I used the laptop over the weekend just gone and when I turned it on this morning (Monday 1st August) the TPM was gone and I had to enter the BitLocker recovery key.

I tried updating to BIOS 1.2.10 and nothing changed.  I also tried reverting to BIOS 1.1.15 and it still did not work.

I honestly suspect Dell has forcibly disabled the TPM chip in this device due to accidentally enabling it when they did not intend to do so in the first place as it is not a "business" device.  This seriously pisses me off because I use it for work and part of the reason I bought it was because I knew TPM worked (after checking other owners for their experiences).

Here is my experience just today.  I have a XPS 15 9550.  Got the Dell Update Utility message to update the BIOS.  I went, "sure go ahead".  Looked like it worked fine but when it came time to boot Windows all I got was a blank blue screen for about 1 min then the laptop just turns off.

I tried changing the Boot Mode to UEFI with Secure Boot off but no help

I booted off my recover USB flash drive I luckily made.  Startup Repair failed.  Restore Point failed.

I final thought of Bitlocker being an issue and brought up the Command Prompt and use manage-bde to decrypt the drive.  ***.  It now boots.

I then re-encrypted with BL and rebooted several times and it works.   Then I remembered Secure Boot was off so I turned it back on.  Now it will not boot again.  

I turned Secure Boot back off and booted.  Then decrypted the drive again.  Then rebooted with Secure Boot on.  It worked.  I re-encrypted with Secure Boot on and then rebooted.  Now all works again as expected.

My guess is the BIOS update is wiping the TPM.

Article here http://www.dell.com/support/article/us/en/19/SLN153694/en

BIOS available here http://www.dell.com/support/home/us/en/04/Drivers/DriversDetails?driverId=8800M

Sorry guys but none of these posts are helping.  I had no issues flashing the BIOS either back to 1.1.15 or back up to 1.2.10.  The problem is that the TPM hardware device is GONE from Device Manager.  Without the TPM, BitLocker won't encrypt the drive.

If I go into Device Manager there is no "Security Devices" item in the list, which is where the TPM chip was previously.

I was told to do a power cycle of the laptop: Remove the battery, remove the memory sticks and finally press the power button for a good 30 seconds. Then wait another 30 seconds before you put everything back together.  In another words, just a full CMOS reset. But it worked! After booting the TPM options were back in "Security" in the BIOS.

Interesting.  I'd go try that right now if it wasn't for the fact I don't have a torx driver that small!

BitLocker can be used without a TPM but it requires additional authentication in the form of Password (or USB key I believe)... http://www.digitalcitizen.life/how-enable-bitlocker-without-tpm-chip-windows-7-windows-8

I had this very issue as well and it happened about 4 weeks after I activated bitlocker. In my case, I had upgraded to Win 10 pro just to get bitlocker. I suspended the protection. After a few weeks of dealing with Dell, they never did resolve it but suggested that I needed a "fresh" full installation of Win 10 pro onto my computer. Before I could take them up on it, I guess because one of the updates I made, the computer came into a mode that it basically forced my into decryption. Once I decrypted, the TPM module showed back up again.

Like the other responder, it was all seemingly pretty random. At this point, I've just left it decrypted since it doesn't seem like I can count on it behaving like it should over time.

Thank you so much for this providing this answer.  If anyone else shows up with this problem, I can confirm that this is in fact a real solution.