I cannot synch a run on my Garmin watch with Garmin Connect. I also cannot manually upload the fit file as it first said it did not support the format type and then said the file has already been uploaded but it does not show up?

If Garmin Connect tells the activity is already there, then I'd try to find it - it may be registered under the wrong (older) date. Try searching at https://connect.garmin.com/modern/activities?activityType=running using the "Advanced" search function by criteria like for example the distance. You could also open the FIT file in Strava or with the FIT File Viewer and see whether the date matches there. You could also look up the activity ID in the FIT file viewer, and then open the activity in GC Web, using the ID in the URL (https://connect.garmin.com/modern/activity/xxxxxxxxxxx)

then said the file has already been uploaded but it does not show up?

If you try to upload it again, you should be able to click on "view details" link, then you'll be directed to the activity that Garmin is claiming already exists.

If you're getting a blank page, then perhaps you can zip then attach your activity here so we can see what might be wrong with it.