Explanation

Since the medium… lacked a voice, it was technology of the day that prevented Lloyd from speaking on film, so the first word should be something like “technological.”

Technical will do. For the second word, you’d like an adjective that would explain why a character would fail to speak, perhaps something like “mute.”

Diffident means something like “self-effacing, very shy.” Reluctant is a bit of a trap answer — it does not mean “reluctant to speak” (the similar-sounding reticent does, and the two words are often confused).

Technical, diffident.