just had a try and it worked well. Could you please check "File Types" in IDEA? Open "Settings" -> type "file types" to search "File Types" setting -> Check "Protocol Buffers file" in "Recognized File Types", make sure "*.proto" is in "Registered Patterns”.
idea安装proto插件后不能识别.proto文件解决方案
原文：https://www.cnblogs.com/dingxu/p/10178654.html
