Statistical Significance Issue in Mixed Model

#1
A multilevel model, with one explanatory variable at the individual level (X) and one explanatory variable at the group level (Z):

\(Y_{ij}=\gamma_{00}+\gamma_{10}X_{ij}+\gamma_{01}Z_{j}+\gamma_{11}X_{ij}Z_{j}+u_{0j}+u_{1j}X_{ij}+e_{ij}\)

correlation between \(u_{0j}\) and \(u_{1j}\) is 0 .

In this pdf , it is written in p.90 that

" The interaction effect of these simulated characteristics are presented in table 4. Tested with a blockwise Bonferroni correction, none of the interactions were statistically significant . "

Bu I found all fixed effect \((\gamma_{00},\gamma_{10},\gamma_{01},\gamma_{11})\) and all random effects \((u_{0j},u_{1j})\) statistically significant except individuals-level residual \((e_{ij})\).

Now my question is if all of them are insignificant according to the mentioned paper , how can the model be valid ? By indicating all of those insignificant , what do they imply ?

Any help is appreciated. Thanks .