That might fix it! You can check whether there happens to be a suitable save in the autosave section.
Though, being on the browser actually makes the following solution a little easier:
Please reload the itch.io page so that the (hopefully) fixed version is properly loaded.
Once you are back in the game, simply reload the save you were using.
Then, choose any interaction and click through the dialogue as usual.
Once you return to the main interaction screen, check whether Myrddin is now in his thinking pose. If he is, simply click on him, and everything should continue from there as intended.
If he still does not enter the thinking pose, please let me know!