Just in case you need information about removing hard drive:

Dell Inspiron 15 3521 Owner's Manual / Removing Hard drive / pages 23 -25

https://www.dell.com/support/home/us/en/19/product-support/product/inspiron-15-3521/docs

Dell Inspiron 15 (3521 / 5521) Hard Drive & Caddy Replacement Video Tutorial

https://youtu.be/3q35j684CQc

If updating or reseating the drive doesn't fix error code, check your warranty status by entering service tag number (or use Detect PC) onto the link below.

Warranty & Contracts

https://www.dell.com/support/home/us/en/04?app=warranty

If there's still warranty on the system, contact Dell Technical Support and ask for a free hard drive replacement in the link below.

Contact Information Dell

https://www.dell.com/support/contents/us/en/04/category/Contact-Information

Since computer is still running windows, update the hard drive ( or  solid state drive) in device manager to see if it will make any difference. You could do this by typing Device Manager onto search box, expand Disk Drives, select Update Driver. Please click on the link below for additional information.

Resolve Hardware Issues With Built-in and Online Diagnostics (ePSA or PSA Error Codes) 

https://www.dell.com/support/article/us/en/04/sln115162/resolve-hardware-issues-with-built-in-and-online-diagnostics-epsa-or-psa-error-codes?lang=en