I have a Dayton gps installed in my car .I cannot access maps etc or put in new addresses .can I reboot or reinstall software?

You'll need to connect your GPS device to a computer (using the USB port), and use the TomTom HOME software to access and download maps from the tomtom website and install it on your device. Then, when you connect your GPS to your computer and run the HOME software, (after you sign in to your TomTom account), the software will identify data, maps, etc. that you can download and install on your TomTom GPS device.
Recently Tomtom has limited support and updates for certain (older) models of TomTom GPS. They hope you'll get a new model. If your TomTom One GPS device is one of those models with little/no support, you're out of luck.

Go to the Garmin website and download and install Garmin Express. Then plug your GPS into your PC. The program will identify the Garmin and you can update/install the maps and software with it. If Garmin Express does not work to solve your problem, you need to contact Garmin Support for warranty work.

Plug your nuvi into your PC. Go to the Garmin.com website and log into your account to see your map information. You can go to your account and see the map downloads and reinstall it from there. Or you can download their software "Garmin Express" on your PC. Run the software while your Garmin is plugged into your PC and it will check for any updates for you.

have you gone to the map information screen and put a check mark in the box next to the France map? This enables the map.

Many Garmin units have a menu item that shows a list of installed maps. The main map is usually located on the GPS's internal memory. Any additional is likely found on the SD card.
When you access the menu / setup and choose maps, you will see both maps. Make sure that you uncheck the map in the main memory (USA perhaps?) and check the map that holds the area you wish to use (Europe?).
When you view the maps on the GPS next time, you should see the maps for the selected area and be prompted for locations that make sense for that area. Simply reverse the steps above to get back to the main internal maps when you return.
I hope this helps!

Go on your gps menu and put in the address or country etc. and see if it works

There's a possibility that the navigation software is corrupted.
Have you tried to recover it from your backup (on your computer) ?
Otherwise, you'll want to use TomTom Home to see if you can download and re-install the software from the tomtom webiste.
Recently, TomTom has decided to limit/stop support (including software/maps, etc.) for certain (older) models of TomTom GPS. If your model is one of those, you're out of luck. TomTom is trying to have you buy a new model.

Download the TomTom Home application and install it on your computer. Connect the unit to the computer, turn it on and when it asks you to connect to computer tap Yes. The Home application will launch and communicate with the GPS. You will have to supply a valid email address and finalize the registration. The update should then be done automatically.

You should update all:

1. Maps: you have a 30 day guarantee on the latest map.
2. The operating system (application).

If for some reason the updates cannot proceed you may be well advised to return the unit for an exchange or a refund as it may be defective.

I have the new N30 software, it has updated maps and updated software. You can input street addresses and via directions. Contact me and I'll give you a link to download it. Joe

Is the correct software installed? Have you attempted any installations on the device and have you downloaded any 'add-ons' such as new voices, etc.
Is it new or bought used?