  Resonance lines of $^7$Be are detected currently in five novae. Available
abundances for this isotope estimated from equivalent widths of $^7$Be\,II and
Ca\,II lines are significantly higher compared to predictions of models for the
thermonuclear flash. In attempt to pinpoint the reason for this disparity we
explore the possibility for the higher $^7$Be yield via computing kinetics of
the thermonuclear burning in the framework of two-zone model and find that even
for a favorable choice of parameters $^7$Be mass fraction does not exceed
$3\cdot10^{-5}$. This is consistent with known theoretical results and leaves
the disparity between the theory and observations unresoved. We find that the
contradiction is caused by the assumption that the ionization fraction of
Be\,II/Be is equal to that of Ca\,II/Ca, which has been adopted formerly in
order to estimate the $^7$Be abundance. In the case of nova V5668 Sgr the
ionization fraction of Be\,II/Be turns out to be at least by a factor of $\sim
10$ higher compared to Ca\,II/Ca due to the difference of ionization
potentials. Our new estimate of the $^7$Be mass fraction for nova V5668 Sgr
does not contradict the theory. The calculated flux of 478 keV gamma-quanta
from the $^7$Be decay is consistent with the upper limit according to {\em
INTEGRAL} observations.
