根據 line api doc

401 就是認證沒過

沒啥好說的

所以你可以檢查你的 token 是否正確無誤

再檢查你的 header 是否格式正確

Authorization: `Bearer ${token}`

附上我測試的 code

不過我是用 nodejs

const Koa = require('koa');
const Router = require('koa-router');
const BodyParser = require('koa-bodyparser');
const axios = require('axios');

const app = new Koa();
const router = new Router();
const port = 9999;
const profileUrl = 'https://api.line.me/v2/bot/profile/';
const token = 'C..FU=';

router.post('/', (ctx) => {
  const { userId } = ctx.request.body.events[0].source;
  ctx.status = 200;
  const headers = {
    Authorization: `Bearer ${token}`,
  };
  axios.default.get(`${profileUrl}${userId}`, { headers })
    .then(res => console.log(res.data))
    .catch(err => console.log(err));
})
app.use(BodyParser());
app.use(router.routes());
app.listen(port, () => {
  console.log(`Server is running at http://127.0.0.1:${port}`);
});

ps.

補充一下

這 api 應該是要用 get

而不是 post

不過這不是造成 401 的 原因就是
補上 python 測試

import requests
access_token = 'C..='
userId = 'U..d'
profile_data = {'Authorization': 'Bearer ' + access_token}

profile = requests.get('https://api.line.me/v2/bot/profile/'+ userId, headers=profile_data)
print(profile.text)