What steps will reproduce the problem?

1. Update to current branch of Bigwigs
2. Log in
3. Multiple Errors

What version of BigWigs are you using? (Stating 'latest' is not useful)

Do you have an error log of what happened?

Message as follows:
1x BigWigs\Locales\enUS-English (US).lua:1: attempt to index global 'BigWigsAPI' (a nil value)
BigWigs\Locales\enUS-English (US).lua:1: in main chunk

Locals:
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = "attempt to index global 'BigWigsAPI' (a nil value)"

Pops errors on English, German, French, Korean, Chinese Simplified and Traditional, Spanish, Russian, ptBR, and itIT

Any additional information? (example: WoW language if not English) (Attach screenshots here if available, do not link externally)

Looks like your install somehow got corrupt.
Delete all the BigWigs folders in your addons folder and then install it fresh.

No response, closing.