The mixture of channels is not a good sign (in general) and the fact that PyMC itself was not installed from the conda-forge channel is further evidence that the suggested instructions were not used (note the -c conda-forge in the instructions). The suggested installation instructions preferentially pull from conda-forge and pulling from a single channel minimizes the chances that conda tries to mix versions and dependencies. If your installation was working but you were relying on locally installed C tool chain ingredients (i.e., not installed via conda) and now something outside your conda env has now changes (e.g., via IT policies), then I guess it’s possible your “working environment” could have stopped working (in the sense that it can no longer find the relevant C pieces and falls back on the much, much slower BLAS implementation). Regardless, environments should generally be disposable and, if they aren’t, it’s a sign that something isn’t quite right.