PyMC 3.11.4 uses theano-pymc 
maybe it would be a good idea to try creting a new environment and installing from scratch to make sure you don鈥檛 have both theano and theano-pymc or incompatible linkings between the two. There are installation instructions in our github wiki: Installation Guide (Linux) 路 pymc-devs/pymc Wiki 路 GitHub (also for mac and windows)