The snapshots attached do not show up.
Invalid master video usually mean that the video linked is not accessible / corrupted.
Please provide the following details so we can check what is causing this:
#1 are you on iOS or Android
#2 has the video been recorded using the internal cam or using an action cam
#3 does the video use a standard format like HD, FullHD, UHD 4K
Android
Recorded using GoPro
Recorded FullHD (1920x1080)
**I should also note my sessions appear to have been split into 3-4GB chunks of video could this error have anything to do with this?
In case your GoPro splits the video into 4GB chunks, merge them using a video editor before transferring it to you smartphone. Except chunk #2 and following may be incomplete in terms of a proper video format and result in this error message. NB: the joined video will be associated with all laps of the video's session.