Past Perfect And Present Perfect In One Sentence

==> Until more recently, Product XYZ had not been ready but Provider XYZ has made changes to the product a while ago that address the issue and
markets are now embracing the product.

Is this sentence grammatically correct? My thinking was:

• 1) Had not been / past perfect --> It is ready ever since Provider
  XYZ has released the product but since that was a while ago its a
  condition that changed in the past before the present.


• 2) Has been /present perfect --> Provider XYZ released a product but
  this release is affecting the present and future and I want to
  underline that by using present perfect. I also don't know the exact moment when they released it.

Thank you for your help, much appreciated. Just wanted to make sure I am using past perfect correctly. At what point would you use "past tense" in a sentence like this? E.g. if you know exactly when the product was released.

Answer

There is no prohibition on using the past perfect and the present perfect in one statement. For example:

Until more recently, Product XYZ had not been ready but Provider XYZ
has now made changes to the product ... .

The problem here lies in the combination of a present tense (the present perfect) with an adjunct of past or finished time (a while ago). This is generally ungrammatical. For example:

*Until more recently, Product XYZ had not been ready but last week Provider XYZ has made changes to the product ... .

*Until more recently, Product XYZ had not been ready but in 2014 Provider XYZ has made changes to the product ... .

While some native speakers might find your original sentence marginally acceptable, you are safer using the past tense (preterite):

Until more recently, Product XYZ had not been ready but Provider XYZ
made changes to the product a while ago that address the issue and markets are now embracing the product.

And if the issue no longer exists, you could put 'address' into the past tense also.

Alternatively, you can replace the past time adjunct with one that extends time into the present and retain the present perfect:

Until more recently, Product XYZ had not been ready but Provider XYZ has
made changes to the product in the past few months that address the issue and markets are now embracing the product.