I just had the same issue, and it turns out it was a permissions issue in the MagicMirror folder, I changed the permissions of the folder and re-authorized, it’s now working.

Best regards

Cannot set headers after they are sent to the client

so, this error is typically caused by some code doing two sends for an incoming request

the module sets up a little server to receive and does a redirect response…

but this could be an async problem
start sending one response, continue while it runs and then fall into another send… oops…

I only made a cursory look at the code. i have done similar things in some of my coding here and on other platforms.

I don’t ‘see’ it, but there is a library in there too

this says it is handling a callback on request complete,

line 185 is in the handling of the token auth . but the stravea lib is calling back into the function (function (err, payload, limits) at line 176
so the node_helper called strava, who called us back at the function on line 185 ( (err, data) => { (err, data) => { ) which does a redirect… WHILE the strava request to get the auth token handler is still active…

			strava.oauth.getToken(authCode, function (err, payload, limits) {
				if (err) {
					console.error(err);
					res.redirect(`/${self.name}/auth/?error=${err}`);
					return;
				}
				// Store tokens
				self.saveToken(clientId, payload.body, (err, data) => {    // line 185
					// redirect route
					res.redirect(`/${self.name}/auth/?status=success`);
				});
			});

line 451, is in the end of the saveFile() function, supposedly to save the tokens.json

	saveToken: function (clientId, token, cb) {
		var self = this;
		this.readTokens();
		// No token for clientId - delete existing
		if (clientId in this.tokens && !token) {
			delete this.tokens[clientId];
		}
		// No clientId in tokens - create stub
		if (!(clientId in this.tokens) && token) {
			this.tokens[clientId] = {};
		}
		// Add token for client
		if (token) {
			this.tokens[clientId].token = token;
		}
		// Save tokens to file
		var json = JSON.stringify(this.tokens, null, 2);
		fs.writeFile(this.tokensFile, json, "utf8", function (error) {
			if (error && cb) {
				cb(error);
			}
			if (cb) {
				cb(null, self.tokens);  // line 451  --- this calls back into the  ( (err, data) =>)  function
			}
		})

at FSReqCallback.oncomplete (node:fs:188:23) {

Note: when I click the authorize button a the Stava auth site after being redirected there from my MM on the RPI, in Electron, I see this generated:

[03.05.2022 10:13.13.537] [ERROR] Whoops! There was an uncaught exception…
[03.05.2022 10:13.13.538] [ERROR] Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
at new NodeError (node:internal/errors:371:5)
at ServerResponse.setHeader (node:_http_outgoing:576:11)
at ServerResponse.header (/home/jberk1984/MagicMirror/node_modules/express/lib/response.js:776:10)
at ServerResponse.location (/home/jberk1984/MagicMirror/node_modules/express/lib/response.js:893:15)
at ServerResponse.redirect (/home/jberk1984/MagicMirror/node_modules/express/lib/response.js:931:18)
at /home/jberk1984/MagicMirror/modules/MMM-Strava/node_helper.js:185:10
at /home/jberk1984/MagicMirror/modules/MMM-Strava/node_helper.js:451:5
at node:fs:2122:7
at FSReqCallback.oncomplete (node:fs:188:23) {
code: ‘ERR_HTTP_HEADERS_SENT’

So the issue seems to be whatever is causing that. I never do see the token.js being generated after clicking the authorize button. My client and secret ID are correct in my config.js file (can’t tell you how many times I have checked to make sure)

• yes npm install was run the MMM-Strave folder
• yes I did the browser auth on the RPI as well
• no, I do not see a tokens file in the MMM-Strava folder after attempting the authorization:
  

• Have run npm install in the MMM-Strava folder?

• Did you do the browser auth on the PI?

• Does the tokens.json file exist in the MMM-Strava folder and does it have the required information in it? This should be created once the authorization step has been completed from the Browser on the RPi and should be populated with some token and user information.
  

Other than checking that I am not sure what else you can check. Other than starting the process from scratch to re-install and re-auth I don’t know what else you can do.

{
                        module: "MMM-Strava",
                        header: "My STRAVA Stats",
                        position: "middle_center",
                        config: {
                                        client_id: "your_client_id",
                                        client_secret: "your_client_secret"
                                        activities: ["ride", "run", "swim"],
                                        period: "all",
                                        stats: ["count", "distance", "achievements"],
                                        units: "metric",
                                        updateInterval: 86400000,
                                        reloadInterval: 86400000

I am using address: “0.0.0.0” and I am not having any issues.

No luck though. I see lots of errors with Dev tools from PiHole module if I change from 0.0.0.0 to the IP of the RPI4

change to the ip address of the pi

address:“191.168.?.?”

and try again

Note: I have my pihole disabled while testing, as it is also on this RPI