Your suggestion to remove the  mobo battery did the trick. When I checked the battery, it was completely dead. That surprised me a the computer/battery is only 18 months old and it did not shown any of the typical signs (not keeping date and time info, language settings) associated with a bad battery. or maybe i just didn't notice them. Anyway, device security in Windows now says I'm protected with a TPM module, as it did before. Interestingly, the bios does indicate its a PTT module and its turned on. So is secure boot. So my problem appears to be resolved with a battery change. Thanks for all your suggestions.
My XPS 8940 desktop is giving me an error message on boot "TPM device not detected". There is no TPM settings in the  bios anymore and Windows security and the device manager do not show it. It's just gone! The PC had TPM enabled when I got it in November 2020 as I checked the status before upgrading from Windows 10 to 11 this winter. No issues running Windows 11. I updated to the current BIOS 2.4.0 in February or March of this year and the error message started shortly thereafter. Is there a bug in the current BIOS? Can I simply re-flash the current BIOS or can I go back to a previous BIOS version? Or can I restore the BIOS setting to their default  or factory settings? Would any of these actions get the TPM back? Or do I just wait until Dell releases a new BIOS and hope that corrects this issue? Please give me some suggestions.
XPS 8940, TPM device has disappeared