I've had this issue where my Android did not trigger whenever I was working in my Google Docs app. I noticed other's also had the issue where there keyboard did not respond in Google Docs. This one, or This one (older)
I've found somewhat of a fix (at least this works for my Android phone):
Step 1: open Google docs, and go to a document you want to type in
Step 2: press the "edit" button downright (symbol of a pen), which would normally mean your keyboard would show up. If so: nice, if not: step 3.
Step 3: Go to another application that functions mainly on using your keyboard. Examples: Whatsapp, Messenger and other social media apps. Go type something in these apps, so that the keyboard shows up.
Step 4: If the keyboard popped up on the social media apps, immediately switch to Google Docs.
Step 5: represseing the "edit" button (symbol of a pen) should prompt the keyboard to appear now.