I have linked the TATTA app to my Epson View / NeoRun device, but my running data is not reflected.

It can take some time before your data is reflected.
On TATTA, only data measured by your EPSON running watch after you have established the link to the Epson View / NeoRun app will be recorded, and no data measured by your EPSON running watch before you have established the link to the Epson View / NeoRun app will be recorded.
Your running data from your EPSON running watch will be linked to TATTA not when you have saved your records on your EPSON running watch, but after you have established a link to the Epson View / RunConnect (NeoRun) app.