If the presentation is important for you you should do whatever possible to be prepared for extreme situations. What you can do?
- Do presentation in your office
- Install your product on the laptop if possible
Even in such case the presentation sometimes goes wrong. You cannot fight yourselves quality of your infrastructure and tools available to show customer result of your work. If such problems are regular your Scrum master should escalate them and they should be solved by management (increasing quality of infrastructure, providing better mobile internet connection or whatever else).
If the problem happens rarely customer will most probably understand (unless relations with customer are already in bad condition). It will result in postponing the meeting or replanning the meeting to another day (as soon as possible). This is bad but it is not as bad as skipping the whole meeting. If this happens often customer will not be so kind and it will negatively affect your partnership.
If the problem is in device configuration you should solve this before customer even comes. Messing with computer and trying to connect to your VPN while customer is already on the meeting doesn't look good.
May be the client (who is "part" of
the team) will understand?
Client is usually not part of the team. Even product owner is usually not considered as a part of the team and sprint review is not (should not be) for product owner. Product owner should participate with team during whole sprint so she should already know what has been done. Moreover she should be the one who say that feature / user story is done and can be presented on sprint review. Sprint review is for customer representatives, stakeholders / managers and perhaps also for selected end users, etc.