Runner fails to tag - dead ball is called....???

[Tru_in_Blu]

How about USA 8.7.F
Effect 3
(Dead ball appeal) Once the ball has been returned to the infield and time is called, any coach or infielder, with or without possession of the the ball , may make a verbal appeal on a runner missing a base or leaving a base too soon on a caught fly ball. No runner may leave a base during this period as the ball remains dead until the next pitch.

So RS#1.C.3 states:
The dead ball appeal may be made:
Once all runners have completed their advancement and time has been called. Runners must be give ample opportunity, in the umpire's judgment, to complete their base running responsibilities.

In this case, the runner completing their responsibilities would involve not "advancement", but retreating to the previous base in order to legally tag up.

I think the "giving of ample opportunity" may refer to the period of time BEFORE the umpire calls time.

So even if the PU had perhaps called time a bit prematurely, it would seem that once time had been called, that the runner would not be able to return to first base during the dead ball period.