MSC temporarily not reachable

UE attach with LTE network as "Combined EPS/IMSI" then getting EPS only attach from network. EMM cause comes as "MSC temporarily not reachable". What will be the UE behaviour after getting this?

This behaviour defined in 24.301. 
This is a temporary reject cause. So when this reject cause is received following is the behaviour: 
1) Increment attempt counter by 1. Start T3411. 
2) After expiry of T3411 attempt combined TA/LA update. 
3) If successful, continue with normal operation. 
3) Else if the same reject cause is received and attempt counter is less than 5, go back to step 1.
4) If attempt counter is greater than or equal to 5, then the next behaviour depends on the UE mode of operation and the status of IMS registration. 

If IMS registration is successful, then stay on LTE irrespective of the UE mode of operation. 
If IMS registration has failed/not supported: 
a) If UE is in CS/PS mode 1(voice centric) of operation, disable LTE for operator determined duration and move to legacy (2G/3G), since voice is our priority. Generally the disable duration is the duration of T3402. 
b) If it is in CS/PS Mode 2(data centric) of operation, then stay in LTE and attempt combined registration after expiry of T3402.