I can't use Macros in Microsoft Office 365

Question

Hello, good morning. I hope you are doing well. I'm writing to you because I created a program with macros to use it simultaneously on three computers for a project. We subscribed to Microsoft Office 365 Family so that all accounts have Office 365 and we can work together. However, when I try to open the file in the desktop application, I get the following message: "Microsoft has blocked the execution of macros because the source of this file is not trusted." To address this issue, I looked for solutions and found that in the Trust Center, it was necessary to "Enable all VBA macros (not recommended; potentially unsafe code can run)," as well as check the option "Trust access to the VBA project object model" and "Enable Excel 4.0 macros when VBA macros are enabled," but I didn't get any positive results.

On another note, I found that it's possible to resolve this by digitally signing the document. To do this, I need to obtain a digital certificate or open the "Selfcert.exe" file located in "C:\Program Files\Microsoft Office\root\Office16." However, when I try to open it, I receive the message: "The application could not start correctly (0xc0000142). Click OK to close it."

I haven't been able to find useful information on how to obtain a digital certificate, which I understand might be free. Therefore, I would appreciate a detailed, step-by-step guide on how to obtain a digital certificate and sign files with macros so that they can be used simultaneously by multiple team members with Office 365.

Thank you in advance.