Welcome to HFH.
Do you have the original UBP-x800, or the Mk. 2 version?
I believe only the original x800 had the Spotify app in N. America, but I'm not sure if that was the case in other regions such as the U.K. There were also various troubles over the years with Sony firmware updates wiping some apps from the menu, and in some cases the only way to get them restored was to do a factory reset which is annoying and a little nerve wracking too if the unit is now out of warranty, however that should resolve it assuming Spotify is still offered by Sony in your region.
The x800 Mk.2 did not have the Spotify app nor can it be installed to the best of my knowledge, but you could add it to your repertoire using something as inexpensive as the
Chromecast with Google TV, however that would have to flow through a TV, or an HDMI audio extractor, and possibly be limited to Toslink output to the E30 in that scenario depending on the exact setup in use.
