just so you know google voice is a telephone service so i do not know how that has replaced your keyboard.
would help to know what device you have? what keyboard are you using? speech to text? as in using your messaging app? some apps will rely on their own speech to text technology. while others will rely on Bixby (if you own a sammy device) or google assistant and some will rely on the keyboard.
can you provide more context as to what is going on? just remember, the more details we get, the better we can help you.
Let me be more specific. I'm using a Moto 6 running Android 9. My keyboard was opening just fine anytime I needed to enter text. I then made the mistake of tapping the mic icon which replaced the keyboard with the Google voice-to-text feature. (I don't call it an "app" since its built into the phone.) The problem is that once this switch happens you can't get the keyboard back! Turning off the phone doesn't work. The Google "Voice Typing" feature has NO setting that lets you reset the keyboard as the default.
Thanks, your solution worked but it took a while to determine that my "app" was "Gboard". You don't actually "open" this app. You locate it in your app list and then tap "storage" which takes you to a screen where there's a "clear cache" button.
I can't believe that the Android experts haven't designed a easier way of getting back to your keyboard from the voice setting!