Does Reddit block an HttpClient after too many requests?

Good morning
I wrote a discord bot with the function to pull content from Reddit.
About 3 weeks ago, when I last used it, everything was working fine.
Meanwhile I get this exception:

Error: Response status code does not indicate success: 403 (Blocked).

Blocking the IP is unlikely since I tried it with a VPN and from a different physical location.

I get kicked out on the second line:

 var client = new HttpClient();                var result = await client.GetStringAsync($" https://reddit.com/r/ {subreddit ?? "dankmemes"}/random.json?limit=1");

Does anyone have any idea why this is happening? The command is usually spammed a lot…
Maybe that's why something was blocked?
Maybe you know a better way to do this?
Thanks in advance!

"Complete" code:

 var client = new HttpClient();                var result = await client.GetStringAsync($" https://reddit.com/r/ {subreddit ?? "dankmemes"}/random.json?limit=1");                if (!result.StartsWith("["))                {                    await Context.Channel.SendMessageAsync("Subreddit doesn't exist...");                    return;                }                JArray arr = JArray.Parse(result);                JObject post = JObject.Parse(arr[0]["data"]["children"][0]["data"].ToString());                var builder = new EmbedBuilder()                    .WithImageUrl(post["url"].ToString())                    .WithColor(new Color(0, 0, 255))                    .WithTitle(post["title"].ToString())                    .WithUrl(" https://reddit.com/ " + post["permalink"].ToString())                    .WithFooter($"🗨 {post["num_comments"]} ⬆️ {post["ups"]}");                var embed = builder.Build();                await Context.Channel.SendMessageAsync(null, false, embed);