i suffer from the same problem. unsubscribed, reinstalled insurgency and subscribed again. Still same prob.

same problem here, tried the same attempts at fixing it but no luck so far.
(snd_restart doenst work either for me )

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EDIT:

unsubscribing and re-subscribing did not work however manualy deleting the mod and than cache verification fixed it. i have gun sound again.

1. the map were day of infamy is located is called: 601757902
(it is located at: steamapps\workshop\content\222880\601757902 and not in the same place as Insurgency the game is)

2. Delete everything in it

3. now you will have to verify the integrity of the game cache (make sure you are still subscribed to this mod)

4. after the verification a download should start with a size of ~200 MB

5. After the download is complete re-start Insurgency

hope this helped for others too

Same issue, ive tried everything. Do you know where I can find the DOI files in insurgency?

Deleting "SteamApps/workshop/content/222880/601757902/doi.vpk.sound.cache" should be enough to fix this problem. Steps 2-5 do not seem to be necessary.