A common configuration is establishing a Google Voice number which will forward to an Aircall number. This is typically done as Google Voice does not offer an IVR service on certain tiers of their service. Unfortunately free Google Voice numbers are not designed for business-use cases.
Google Voice is configured in such a way that it will flag a call if it is answered too quickly. If you answer a Google Voice call instantly, there is a message that plays that says "You answered too quickly, we want to make sure it's legit, please press a button."
Inbound calls to Aircall numbers configured with an IVR or Audio widget will normally answer before the completion of the first ring, which has proven to be too quick for the Google Voice configuration. The introduction of a slight delay (~2 seconds) would allow these calls to complete successfully, but this delay is limited to the higher tiers of Google Voice accounts.