For anyone struggling with getting the reram model to work in xyce, if you have access to Hspice or Spectre, you can use the hspice model I created from the ngspice models. The hspice model is available at
https://github.com/lekez2005/open_pdks/releases. Just download and extract the hspice-models.tar.bz2. Hspice/Spectre can correctly (at least qualitatively) simulate switching and read behaviors modeled in the Verilog-A model