If anyone is still having this issue, can you please let me know if you're seeing the Windows Boot Manager and Disk Drive listed under the Boot Sequence in the BIOS? This can vary depending on system model but here is an example of what it could look like:

To enter the BIOS, press F2 at the Dell Screen before Windows attempts to boot and then select Boot Sequence (this could also be referred to as Boot Order).

If you're still having this issue, please try resetting your BIOS to default. Be careful using this solution if you have made changes to your BIOS as you will need to make them again.

Here is a helpful video for resetting the BIOS: 

Marking as Dell Solution for visibility, please note there could be other reasons the system is getting this message but I wanted to provide a solution that has worked for some users. 

Hello, I see you are looking for technical assistance. If you need our help, you can start a private/direct message with us and we will be happy to assist you.

Did anybody help you about this?

I have the same Problem

Dell has released a few remediations and mitigations for users. Users can further protect themselves by following these recommendations.

Users have been asked to use secured networks and prevent unauthorized local and physical access to devices.
Dell has asked the users to enable platform security features such as Secure Boot and BIOS Admin Password for additional protection.
No action required on CVE-2021-21573 and CVE-2021-21574 as these two vulnerabilities were remediated on 28th May, 2021.
The other two CVE-2021-21571 and CVE-2021-21572 vulnerabilities would require system BIOS updates to address the vulnerabilities. Please check out the affected device table from the post to find out the required BIOS version.
Users can’t go with BIOS updates immediately. They can disable the BIOSConnect and HTTPS Boot feature on the system BIOS.

I have reset my bios and the only boot option I see is:

UEFI HTTPs Boot

Hi . only Htpps / ipv4 / ilv6

no others options 

pls

help me

I have loaded defaults in bios,  still it shows that https boot failed to intialize network connection 

All,

Please try this and let me know if it fixed the issue for you:

1. Reach to BIOS set up by pressing “F2” when system boots.
2. Click “Boot Configuration” uncheck all options except for the internal SSD/HDD (blue rectangle in the pic below). The click “Apply changes” and exit.
3. If SSD/HDD options are not available, restore the BIOS to defaults (Load Defaults).
4. Check if it will boot to your operating system.
5. If it doesn't boot, try reseating the HDD/SSD (unplug/remove and plug it back in again). This step might be complex if you're not familiarized with hardware, so make sure you read your system manual and contact Dell if you need a technician's help. Data loss risk, so please make sure you save all your important files.
6. Reboot your system and try to boot again.
7. If the error changes to “No bootable device”, then you need to Restore your Computer Using SupportAssist OS Recovery or reinstall the OS.
8. After the OS recover/reinstall you should be able to boot normally.
9. If you still need help, please contact the support by clicking on Get Help Now on the bottom right corner of this page. Provide to them the private computer Service Tag and all of your troubleshooting.