Can't load tokenizer for 'bert-base-multilingual-cased'

[Ning0719]

When I use droidbot, once I adopt a machine learning strategy, an error will be reported, prompting: “Can't load tokenizer for 'bert-base-multilingual-cased'. If you were trying to load it from 'https://huggingface.co/models', make sure you don't have a local directory with the same name. Otherwise, make sure 'bert-base-multilingual-cased' is the correct path to a directory containing all relevant files for a BertTokenizer tokenizer.”
I want to know why and how to solve this?