Can not open file in time capsule.

Post a screenshot from your Airport Utility.. showing the TC summary page.

This one. So we can give you exact instructions. I will see if Bob is around as I refuse to load a buggy OS like Sierra into the computer.

IMHO for now.. you might be better copying all your files to a USB drive.. plug that into your laptop and play your files locally NOT over wireless.

Since you are using your TC solely for file storage you do not need to connect LAN or WAN.. but of course while connected to the TC you have no internet which is kinda messy.

In Finder.. use Go, Connect to server.

Type in the address. As follows.

The computer will search for the TC and will ask for your disk access password.. type that in and make sure you save to keychain..

You should now be able to open the file.

This is a Sierra bug.

There is a work around.. Bob Timmons discovered it.

Use manual mounting in Finder.. via SMB.

eg SMB://10.0.1.1 (replace with the actual IP of your TC).

You will be asked for the admin password to your TC.. this is the Disk access or main password... remember to save it in the keychain.

How does that go??

Look up posts with error 36.. as this is commonly reported now.

And running live files from a TC is definitely not a great idea. You might find it very slow.. cf earlier OS due to Apple increasing security. There is also a way to improve SMB speed.. discovered by Tesserax.

If you can use AFP but not SMB to mount a file server - Apple Support

SMB speed is greatly increased by removing the signing.