Why does it take longer than 48 hours for electronic returns to be accepted through TT?

See this TurboTax support FAQ if your e-filed tax return is pending - https://ttlc.intuit.com/turbotax-support/en-us/help-article/taxation/return-still-pending/L2Z5h8ehz_US_en_US?uid=l97q3ebd

The delay at this time is an IRS issue and is affecting more than just TT returns.  This is especially normal at this time of the filing season as millions funnel into the que in the last few days.