Forza 4: my car slows down.

Three days ago I bought the Forza Horizon 4 for PC, and I have a big problem: the car does not accelerate.
The game starts well, I enter the menu and everything, but when I have to run my first exhibition race the car starts but slows down by itself, even if I keep pressing the advance key.
I tried changing the configuration of the keys but the problem persists and it becomes impossible to play like that since I cannot win any race because obviously my car DOES NOT SPEED.
Here is a link to a video about the problem: Forza problem
I have Windows 10 Pro, 1903 64 bit version. Intel Core i5, 16gb RAM and NVIDIA Ge Force 950 video card.
ALL updated drivers.

I hope for a possible solution. Greetings from Argentina.

Things I would check before logging ticket
have you enabled the damages in your car difficulty settings ?
not tested but, try windows+CTRL+O to display virtual keyboard, not sure it works but it could help you to confirm an issue with your keyboard.
Make sure you don’t have any accessibility settings enabled like the one managing repetition of pressed key (filter key )
accessibility setting

check your settings too and make sure assisted braking is off

Check if you have Assisted Braking turned on. That causes the car to auto-brake in corners.

Oddly enough I’ve noticed a similar thing but only in Online Ranked play…
I’m playing a PC version of Forza Horizon.
I can drive and race without issue, even with coop races and yet in the last few days when I switch to a ranked race, my race starts well but quickly devolves into a car that keeps changing down gears and only intermittently accelerating - at first I thought that it was my controller - but exiting from an Online adventure/ ranked race sees my car behaviour return to normal.

Well I’ve fixed my problem - thanks for the hint.

The issue that I had was that somehow “Assisted Braking” was turned on.

This may not normally be an issue, but with Traction Control turned off it would appear that any form of wheel spin will cause the car to brake hideously hard just about all the time and guess what, my Online Ranked races were all Winter Season and yet my other races were all Autumn.