You don't need to pull out your hair anymore in an attempt to compile a correct CA Bundle for your certificate! We already did that for you.

If you have your certificate in the PKCS#7 format (appropriate mostly for IIS/Microsoft Exchange), you already have your bundle included into your certificate and do not need to install it separately.

In order to save the file it is necessary to right-click on it and use the 'save as' option. Otherwise, your browser may try to install it.

Keep in mind that Sectigo (former Comodo) CA currently has several versions of the "USERTrust RSA Certification Authority" SHA-2 root certificate.

The up-to-date version is not cross-signed by any other certificate and is a self-signed SHA2 root certificate in fact. Another valid version is cross-signed by the AAA Root certificate.

      New Sectigo Bundles under SHA2 Root certificates (not cross-signed):

Sectigo RSA Domain Validation under SHA-2 root (valid for PositiveSSL, EssentialSSL, PositiveSSL Multi-Domain, PositiveSSL Wildcard and EssentialSSL Wildcard certificates)
contains:

• Sectigo RSA Domain Validation Secure Server CA [ Intermediate ]
• USERTrust RSA Certification Authority

Sectigo RSA Organization Validation under SHA-2 root (valid for InstantSSL, InstantSSL Pro, PremiumSSL, Multi-Domain SSL, Unified Communications and PremiumSSL Wildcard certificates)
contains:

• Sectigo RSA Organization Validation Secure Server CA [ Intermediate ]
• USERTrust RSA Certification Authority

Sectigo RSA Extended Validation under SHA-2 root (valid for EV SSL and EV Multi-Domain SSL certificates)
contains:

• Sectigo RSA Extended Validation Secure Server CA [ Intermediate ]
• USERTrust RSA Certification Authority

Sectigo ECC Domain Validation under SHA-2 root (valid for PositiveSSL, EssentialSSL, PositiveSSL Multi-Domain, PositiveSSL Wildcard and EssentialSSL Wildcard certificates)
contains:

• Sectigo ECC Domain Validation Secure Server CA [ Intermediate ]
• USERTrust ECC Certification Authority
  

Sectigo ECC Organization Validation under SHA-2 root (valid for InstantSSL, InstantSSL Pro, PremiumSSL, Multi-Domain SSL, Unified Communications and PremiumSSL Wildcard certificates)
contains:

• Sectigo ECC Organization Validation Secure Server CA [ Intermediate ]
• USERTrust ECC Certification Authority
  

Sectigo ECC Extended Validation under SHA-2 root (valid for EV SSL and EV Multi-Domain SSL certificates)
contains:

• Sectigo ECC Extended Validation Secure Server CA [ Intermediate ]
• USERTrust ECC Certification Authority
  

New Sectigo SHA2 Bundles under AAA Root

RSA DV Bundle under AAA Root (valid for PositiveSSL, EssentialSSL, PositiveSSL Multi-Domain, PositiveSSL Wildcard and EssentialSSL Wildcard certificates)
contains:

• Sectigo RSA Domain Validation Secure Server CA (intermediate)
• USERTrust RSA Certification Authority
• AAA Certificate Services (root)

RSA OV Bundle under AAA Root (valid for InstantSSL, InstantSSL Pro, PremiumSSL, Multi-Domain SSL, Unified Communications and PremiumSSL Wildcard certificates)
contains:

• Sectigo RSA Organization Validation Secure Server CA (intermediate)
• USERTrust RSA Certification Authority
• AAA Certificate Services (root)

RSA EV Bundle under AAA Root (valid for EV SSL and EV Multi-Domain SSL certificates)
contains:

• Sectigo RSA Extended Validation Secure Server CA (intermediate)
• USERTrust RSA Certification Authority
• AAA Certificate Services (root)

ECC DV Bundle under AAA Root (valid for PositiveSSL, EssentialSSL, PositiveSSL Multi-Domain, PositiveSSL Wildcard and EssentialSSL Wildcard certificates)
contains:

• Sectigo ECC Domain Validation Secure Server CA (intermediate)
• USERTrust ECC Certification Authority
• AAA Certificate Services (root)

ECC OV Bundle under AAA Root (valid for InstantSSL, InstantSSL Pro, PremiumSSL, Multi-Domain SSL, Unified Communications and PremiumSSL Wildcard certificates)
contains:

• Sectigo ECC Organization Validation Secure Server CA (intermediate)
• USERTrust ECC Certification Authority
• AAA Certificate Services (root)

ECC EV Bundle under AAA Root (valid for EV SSL and EV Multi-Domain SSL certificates)
contains:

• Sectigo ECC Extended Validation Secure Server CA (intermediate)
• USERTrust ECC Certification Authority
• AAA Certificate Services (root)

Legacy Bundles

     Comodo SHA2 Bundles under SHA2 Root

Comodo Domain Validated SHA-2 under SHA-2 root
Comodo Organization Validation SHA-2 under SHA-2 root
Comodo Extended Validation SHA-2 under SHA-2 root
Comodo ECC Domain Validation
Comodo ECC Organization Validation
Comodo ECC Extended Validation