[Samsung Galaxy S8+ Questions & Answers] paul_59:
Glad to hear your problem is now solved.

For general information however, with apologies to anyone who is aware of the following:

When any mobile phone can't get or loses a signal it's often assumed to be the phone hardware, it may be at times, other times it could be phone software or interactions between phone hardware and software.

Restarting the phone or enabling airplane mode then disabling will often bring back the signal as original poster found.

The phone working on another networks, by swapping sim can be another clue that the problem might have been with the original network.

Because most of the time mobile phones simply work we can sometimes forget that they are mobile radio transceivers that connect via signals to base stations.

The signal strengths will vary depending on distance from base station and more importantly depending on atmospheric conditions, sun spot activity, weather. Additionally your phone will normally negotiate a connection to the strongest base station signal, if however this base station is not active due to maintenance or hardware failure the phone will attempt to connect to the next strongest signal which may be a marginal signal strength.

Many factors can effect signal connectivity, those referred to above are only a few of the total.

There are free apps that can display more detailed information about which cell towers (base stations) are active in your area and what the signal strength is at your location and which tower your phone is currently connected to.

Anyone interested can observe how even when your phone is stationary it can sometimes drop connection to one tower and immediately connect to an adjacent tower if that tower is operating and within range.

---------- Post added at 05:16 PM ---------- Previous post was at 05:15 PM ----------

Glad to hear your problem is now solved.

For general information however, with apologies to anyone who is aware of the following:

When any mobile phone can't get or loses a signal it's often assumed to be the phone hardware, it may be at times, other times it could be phone software or interactions between phone hardware and software.

Restarting the phone or enabling airplane mode then disabling will often bring back the signal as original poster found.

The phone working on another networks, by swapping sim can be another clue that the problem might have been with the original network.

Because most of the time mobile phones simply work we can sometimes forget that they are mobile radio transceivers that connect via signals to base stations.

The signal strengths will vary depending on distance from base station and more importantly depending on atmospheric conditions, sun spot activity, weather. Additionally your phone will normally negotiate a connection to the strongest base station signal, if however this base station is not active due to maintenance or hardware failure the phone will attempt to connect to the next strongest signal which may be a marginal signal strength.

Many factors can effect signal connectivity, those referred to above are only a few of the total.

There are free apps that can display more detailed information about which cell towers (base stations) are active in your area and what the signal strength is at your location and which tower your phone is currently connected to.

Anyone interested can observe how even when your phone is stationary it can sometimes drop connection to one tower and immediately connect to an adjacent tower if that tower is operating and within range.