Please try the paid version if you can not see "Remote Wave" when you open attachment from your email clients.

Play GSM/WAV/AU voicemail attachment.
Support following encodings:

ULaw(MULaw)
GSM6.1
IMA/MS/Dialogic/OKI ADPCM
DSP TrueSpeech

*** Attention:
Must work with other apps, In email,browser, etc, Press file->"open with"->"Remote Wave".

If your wav file was opened directly by another app, you are setting that app as a default player for .wav files. Please go to that app settings, and "clear default":

https://support.google.com/android/answer/9415055?hl=en