The Spanish path has to run end to end, including the confirmation email
A translated homepage attached to an English form, an English error message and an English autoresponder is not a Spanish path, it is a trap.
Follow the whole route as a Spanish-speaking visitor would: landing page, matter page, form labels, validation messages, the thank you screen, the automatic reply, the calendar invitation, the intake questionnaire that arrives afterward. Every one of those either exists in Spanish or the path breaks.
Breakage is not neutral. Someone who filled in a form in Spanish and received an English confirmation now doubts whether the firm can handle the call, and that doubt costs you the matter after you already paid to acquire the click.
Give the Spanish version its own addresses rather than swapping content at the same URL, so it can be linked, shared with a relative and found in search. Make the language switch a plain link in the header, visible without scrolling.
Chat widgets and callback tools need the same treatment. A chat that greets in Spanish and then hands over to an English-only script is worse than no chat.