Personal records not updating

This means that I'd need to do those EXACT distances for it to register a new personal best?!

Only if you want Garmin Connect to (automatically) figure out on its own that you have achieved a new personal record. There are alternatives:

• You can ‘tell’ Garmin Connect you have achieved a new personal record, by manually designating a tracked activity as such for a selected distance. In that case, Garmin Connect will neither perform any sanity checking (so you could, for example, select a 4.3km run and set it as your 10km personal record manually), nor will it extract your fastest 5km stretch within a 7km run that you set as your 5km personal record.
  
• You can use a Garmin wearable device that will detect new personal records and advise Garmin Connect of such. In that case, Garmin Connect will perform sanity checking; for example, on my recently purchased Forerunner‑630 (or I could do it on my old Forerunner‑235 after a factory reset), after my first run wearing it, it detected new personal records for 1km, 1mi and 5km (as well as longest run). It then told Garmin Connect of those achievements upon syncing, but Garmin Connect correctly determined that I only actually achieved a new personal record for 5km, because it is aware of twelve months of history about which the FR630 knows nothing.
  

I'm currently wearing a vivosmart HR. Could this be the issue?
I would have thought that once the data uploaded to the app, it would update my new personal records for the categories in the app?
Thanks for responding so quickly!!

I'm currently wearing a vivosmart HR. Could this be the issue?

The vívosmart‑HR cannot detect new personal records on its own (whereas the vívosmart‑HR+ can, as can the vívoactive‑HR and Forerunner watches). My best guess is that on-board GPS is a prerequisite for the feature.

I would have thought that once the data uploaded to the app,

Not the app (i.e. Garmin Connect Mobile, running on your mobile phone handset or tablet device) per se, but the cloud-based Garmin Connect service/platform.

it would update my new personal records for the categories in the app?

As you've already noted, Garmin Connect will detect a new personal record (i.e. without being explicitly ‘told’ by either the wearable device or its user) only if the distance of the uploaded run activity record matches one of the predetermined distances (1km, 1mi, 5km, etc.). It is not going to review the activity, data point by data point, to work out which 1km stretch in (say) a 7km run was the fastest, and then test that against the current 1km personal record to see if a new personal record has been achieved, and so on.

Ok I think I understand! Thank you so much for your help :)

Another question on the same topic

I thought it might be relevant to ask the question in this thread rather than creating a new one.

So I ran my Half-marathon with a personal best. Official results was different by 1 second, so after uploading I edited it. Then I struggled with connecting it to my Personal Best. Then, finally, I found a little questionmark icon which explained that edited results will not be connected. (Same as per the screenshot above in the thread.)

So now I cannot connect the race to my Personal Best? Do I have to run it again, in opinion of the Garmin team? Please help to connect.

If this is the policy, I can't agree with it. I am uploading my results for me personally, and not for anyone else. Who cares about my slow times? Why these blocks at all? It is mind-boggling to imagine that some runners would wish to cheat here. It is not an official athletics site at all. Who cares?

Anyway, please help now. Maybe I have made a mistake (no easily accessible Help, by the way - thank for keeping us runners in the dark). But now I am punished by my own wristwatch, just because I amended my result to a correct one by one second??

My watch is Forerunner 410. I ran the distance yesterday. Garmin recorded it as 21.41km.

The only thing you could do is delete the activity from Garmin Connect and re-upload. You would have to do that manually through the web site as Garmin Express won't re-sync an activity it thinks it has already synced.

To do so you will have to retrieve the file off the watch. My understanding is that the files are copied to your computer during transfer, so you will need to find them, delete the run from Garmin Connect and re-upload by using the add file option on Garmin Connect.

I'd find the files first before you go deleting anything off Garmin Connect.

Looking at the DC Rainmaker review, the locations is:

C:\users\<user name>\Application Data\Garmin\Devices\<Device ID>\History