Are A) Developing a New script or B) Opening an existing script for updating?

Double-check your system with LR Detect and compare it to the admhelp.microfocus.com/documents/lr/System_Requirements/24.1/LR_System_Requirements.htm to ensure your system has the CPU/RAM etc in line.
 >> Are you a local Admin to perform the Installs? If not, you'll have to re-Install as a member of the Administrators group 
Also, UAC and DEP are known to interfere with TruClient script. I know the primary documentation says you can have it enabled, but in practice it interferes with LoadRunner operation. so that may be contributing. It's listed on Known issues (microfocus.com) so OT is obviously aware of it. Also in practice, If your ability to Record is impacted, your ability to Replay may be impacted.

It's to develop a new script. We've also tried on existing scripts from our other colleagues who have earlier versions of LR and the same thing happens. Disabled the DEP and still nothing. Is there a way to download an older version of LR? 

Hi
Ariana Warren 

It might have to do with virus scanner. TruClient script is started with some extra (local) JS scripts to make recording possible. You might try with your IT department do a quick test to see what happens when anti-virus software is disabled or LRP-install directory is white-listed.

I have the same problem on different computers. DEP is ON since company policy to have it on.
Did you find a solution that works?

I have not turned off virus scanning. I have had a problem with adding new steps to existing scripts, can add 1 step, but then the browser closes.
Looks like mouse click on Left button is causing the problem since I can tab to correct place and add code for more steps.
Quite frustrating for large scripts.

I disabled DEP and UAC, but still get same problems with TruClient scripting. Works fine for a while, but then browser closes. Tested with both Cromium and TruClient Browser. 

I found out that version 2020 SP2 is working fine even if DEP is on, but from 2020 SP3 I get the error as described above.

Do you know if there is a patch or something that makes 2020 SP3 and newer versions work even with DEP on?

RE: 2020 > LoadRunner 2020 is deprecated, end of life. You might, maybe be able to find old resources, but ithere will never be fixes or future development. The availability of LoadRunner 2020 assets is scarce and uneven. That version, unpatched, carries the log4j vulnerability as well. LoadRunner 2021 is EoL Jan2025, and will have the same dearth or resources in a few months. 
In addition, LR 2020 TC 'client' is locked to the version current at that time (what is Installed for you to use is NOT the TC browser). 
 A 5 yr old, unupdated browser can't run your test on the site, argues that it can't handle the server response. It's old. 2020SP3 has IE 11 (IE isn't even a supported browser anymore, anywhere), chromium 80 and TC(FireFox)77. ?Can those browser versions correctly test your site?
This is the primary reason is is best for your environment to keep the LR current.

TruClient, the protocol, has lived a few different iterations. I would have found it easier if it had been versioned as itself or even renamed before now. The version that was in PC/ALM (12.6x and lower to ~11) was a very different protocol than the one used in 2020. It changed again in 2022>2023.
LR 24.3 has a New protocol TruClient2.0, in addition to the updates to the TC. That is 3 very different syntaxes and operations. The oldest form of TC is synchronous commands only. In all guidance from 2020, LR tells us support for Sync Will Be Removed; Use Async. This was the change in 2020, bringing in Async.

The advice from the guides is I think still the best path:
> Replace all synchronous syntax calls with asynchronous. This replicates how users use a browser today. Async Is The Way. Support for synchrnous replay WILL be removed, if it has not already.
> Don't Re-Invent the Wheel, use modern built-in TC commands instead of 'custom code'. there's a TC module to just about anything you need in a TC Browser, it's preoptimized and will run faster and better than something compiled on the fly. Older versions of TC carry a LOT of deprecated, custom code for which there are modern alternatives.
> Re-Test the VUser in the New version, Refactor and perform any other maintenance, and you still may need to Re-Develop/Re-Record the VUser, using net-new version protocol. Sometimes it's easier to build New than to renovate.

If it were my environment, I'd upgrade to the latest (LR 24.3), use the TC and TC 2.0 to decide which of the modern approaches works best for the AUT. Re-Record everything in the winning option.

Hope this advice helps! Happy Testing!!
Robin Haynes

Also, the LoadRunner using TC protocol requires the following in User Rights Assignment: