Hello, Pedro Moreno4.
Welcome to Microsoft Community!
After reading your description, I noticed that you currently seem to be trying to install your Surface Laptop 7 via USB recovery drive.
And the reasons for not being able to boot from USB could be: incorrect startup item settings, and the USB recovery drive was not made correctly to be recognized.
To assist you in mitigating this issue, I will share with you some possible suggestions.
We have no way of knowing how you made the drive, so allow me to describe the process here. First, we need to make sure that the flash drive has been formatted. Please prepare a clean USB flash drive and get the image file for your Surface Laptop 7 from the following site:
Surface Recovery Image Download - Microsoft Support
Get it by logging into your account and entering your device's serial number:
With the above steps, we are done with the USB drive. Then we will proceed to set the correct boot order by referring to the guidelines in the following link:
Boot Surface from a USB device - Microsoft Support
The link provides key textual guidelines and some advice.
These are some of the information I can share with you now.
Please don't hesitate to let me know if you have anything to add to what you need, I'm here to support you.
Best Regards.
Leo.L - Microsoft Community Support Specialist