You will need to clear your Local Storage in order to fix this issue.

For Chrome:
1. Go to Settings > Site Settings > View permissions and data stored across sites > Find  the domain "pf.nutaku.com"
2. Hit either the "X" or click "Indexed Database" > Remove

For Firefox:
1. Open the game, with the error message
2. Go to Tools > Web Developer > Storage Inspector
3. Open Indexed DB > pf.nutaku.com
4. Right click "/idbfs (default)" and click Delete

After that, please refresh the page and the game should load normally.