Coverage is a major concern of any wireless network to assure its performance. It indicates how effectively the required area is being monitored within a established network. In the existing research, coverage analysis has been done by many authors using different sensing models such as binary and probabilistic models. The binary model ignores channel uncertainty, whereas the probabilistic model considers theses uncertainty that is caused by various external factors and is more realistic. However, Coverage Reliability (CoRe) has not been explored in the literature yet. CoRe determines the considerable period of time to which a network provides the required coverage. This paper proposed a model to estimate CoRe as for Mean Time to Failure (MTTF) for a wireless network deployed in C-RoI with Multipath Shadowing (MS) effect under sensor failure scenario. The analytical model is validated through MATLAB simulation. The impact of various parameter $viz$ the number of sensors ( $N$ ) sensing range (SR) $\mathrm{r}_{\mathrm{m}}$ , and MS effect has been analyzed for coverage and CoRe and a consistency has been found in the result.